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3 



>/ 



en H 



THE STRUCTURE OF MAN 






♦ 



^ 



THE 



STEUCTUEE OF MAN 



AN INDEX TO HIS PAST HISTORY 



Dk. e.' wiedeesheim 

PROFESSOR IN THE UNIVERSITY OF FREIBURG I. BADEN 



TRANSLATED BY 

H. AND M. BEENAED 

THE TRANSLATION EDITED AND ANNOTATED AND 
A PREFACE WRITTEN BY 

G. B. HOWES, r.L.S. 

PROFESSOR OF ZOOLOGY, ROYAL COLLEGE OF SCIENCE, LONDON 



With 105 Figures in the Text 



Honlion 
MACMILLAN AND CO. 

AND NEW YORK 
1895 

All rigHU rewT-oed 



PREFACE 

The circumstances which led to the production of this work in 
the original German are sufiSciently set forth in the annexed 
" Introduction," and no one would admit more readily than* its 
author that it is largely supplementary to the classical treatises 
of Darwin and Huxley, quoted in its pages. Experience of the 
practical method of scientific education has shown that it is 
desirable to place in the hands of the student engaged upon a 
first investigation of individual types of animal structure, some 
sound treatise of a general character, which he may read while 
continuing his more systematic studies. Such works awaken the 
mind to the comparative method of inquiry, and to the higher 
educational and philosophic issues to which it leads. It was this 
consideration which prompted me to suggest this translation, in 
the hope that it might be of use, in the manner indicated, to 
the medical student while engaged in the study of anatomy. I 
am further hopeful that an educated public exists to whom a 
knowledge of the comparative morphology of Man and the 
Anthropoid Apes as set forth in these pages may be acceptable. 

The truth of Evolution in organic nature is now generally 
admitted, but its application to man is not perhaps so widely 
acknowledged. This book, in no sense an exhaustive treatise, 
is an endeavour to set forth the more salient features in the 
anatomy of Man which link him with lower forms, and others 
in that of the lower forms which shed a special light on parts 
of the human organism. Such comparisons furnish a basis upon 
which to exercise judgment concerning Man's position in the 
series of organised beings. 

In dealing with these comparisons, a word of caution is, how- 



vi THE STRUCTURE OF MAN 

ever, needed. Our accepted views as to the inter-relationships 
between the greater groups of animals are largely based upon the 
assumption that similarity of gross structure implies community of 
origin. It is now becoming evident that an essentially similar 
definitive condition may be independently reached, under advanc- 
ing modification along parallel lines, by members of independent 
groups of animals ; and there is reason to suspect that some 
of our classificatory systems are unnatural and erroneous from 
want of appreciation of this principle of "convergence." We must, 
therefore, not lose sight of the possibility that some of the 
characters which modern Man and the higher Apes have in common 
may have been independently acquired. A notable instance is fur- 
nished by the ridges which connect the tubercles of the upper 
molar teeth, described by Huxley and Topinard. On comparing 
the little worn upper molars of, say, a female Chimpanzee and 
Man, one might at first sight be disposed to conclude that modern 
Man has descended from ancestors hardly differing from the 
modern Apes. On comparing the entire Man-Ape series, how- 
ever, it is found that these ridges, and more especially that of 
Topinard, are extremely variable and not infrequently absent in 
individuals of both Men and Apes, and it becomes therefore 
evident that such a conclusion, if not unwarranted, is premature. 
If for no other reason than this, it will be obvious that consider- 
able interest attaches to the more precise determination, in the 
future, of the limits of detailed structural variation in Man 
and the Anthropoid Apes. With regard to variation in Man 
some very useful results have been obtained, during the last five 
years, under the auspices of a " Collective Investigation Com- 
mittee " of the Anatomical Society of Great Britain and Ireland, 
of which I have the honour to be a member. Subjects chosen 
for investigation year by year are taken in hand in the leading 
dissecting roo^s throughout the kingdom. The work of the 
student, becoming thus a research work, is ennobled ; and the 
reports embody a mine of accurate information which, edited 
and tabulated, is of great service to both the surgeon and scientific 
anatomist. 

Our views on some of the topics dealt with in this volume 
may become very much modified as work of the above-mentioned 



PREFACE vii 

order proceeds. There seems, however, no escape from the con- 
clusion that Man and the Apes must have had a common ancestor 
in the i:emote past, and we await with especial interest further 
discoveries of fossil remains which may throw light upon their 
inter-relationships and upon the ancestors of Man. 

Eemains of Early Quaternary Man, few and far between, 
have been unearthed during the last fifty years in England, 
on the European Continent with Gibraltar, and in North America. 
The valley of the Meuse is now famous for having yielded the 
" Naulette " and " Spy " remains, which there is very strong 
evidence for believing to belong to the Palaeolithic Age. The 
salient features of these ancient men are a low retreating and 
contracted forehead and an inwardly shelving occiput (indicative of 
a primitive type of brain and of powerful neck muscles), a high 
temporal ridge and an expanded palate (indicative of powerful 
jaws and jaw muscles) ; and further, the presence of ape -like 
brow ridges (for which the famous Neanderthal calvaria is so 
notorious) appears also to have been a racial character. Dr. 
Eugene Dubois has recently described some remains from the 
banks of the Bengawan Kiver in Java, which he believes to be 
those of a creature structurally intermediate between the types 
represented by modern Man and the modern Anthropoids. In 
this he has been proved by Pettit, Cunningham, Turner, and 
others, to be mistaken. The Bengawan calvaria and the bones 
associated with it are strictly himian. The ca] /^aria shows a 
cephalic breadth index ^ of 70, as compared with 72 for the 
Neanderthal, and its smaller capacity and other characters render 
it perhaps representative of a race more primitive than any 

^ As mentioned in the body of this work {jmfra^ pp. 51 , 52), the cranial capacity 
of the Caucasian may average 1500 c.cm., and that of the Veddah may be but 950 
c.cm. Thirty Australian skulls measured by Turner gave a maximum capacity of 
1514 c.cm. and a minimum of but 930 c.cm., and 100 modem Parisian skulls, worked 
out by Topinard, varied between 1850 c.cm. and 1150 ccm., while Testut describes 
a skull of Quaternary Man from the Dordogne with a capacity of 1730 c.cm. 
Individual variation being thus extensive, it is clear that for purposes of study 
of the inter-relationships between races of mankind, a method which deals with 
relative measurements, in such a way as to eliminate differences due to stature, 
is desirable. The above-named ** cephalic breadth index "method has been found 
to be one of the most serviceable under existing circumstances. It is computed 
as follows : multiply the maximum transverse diameter by 100 and divide by the 
maximum long diameter, as determined by a lino drawn between the superciliary 
ridges and through the most projecting mid-occipital point. 



viii THE STRUCTURE OF MAN 

hitherto discovered During the passage of these pages through 
the press, my friend and colleague, Mr. K T. Newton, has de- 
scribed^ from the Thames Terrace-Gravel, at Galley Hill, in 
Kent, some remains of a human skeleton which there is good 
reason for believing to belong to the Palaeolithic Age, and to be 
perhaps slightly older than the Spy example. The Belgian 
remains were found in caves, those from Galley Hill were em- 
bedded in a Pleistocene river deposit ; and it is a significant fact 
that the skuU of the latter gives a cephalic breadth index of 
but 64. 

The posterior molars or " wisdom teeth " of modern Man are 
exceedingly variable structures (cf. text, p. 159). Even when 
most fully developed, their crowns are as a rule less extensive 
than those of the teeth in front of them. In remains from 
reputed Palaeolithic deposits hitherto described, in which jaws 
and teeth have been preserved, the crowns of the " wisdom teeth " 
are as large as, if not a trifle larger than those of the other 
molars in front of them. This greater development of the last 
molar is characteristic of the oldest known human jaws, but is 
only very rarely met with in those of recent Man. In its most 
expanded condition the crown of the wisdom tooth of both 
recent and fossil Man may be beset by numerous tubercles, its 
posterior and external cusps being subdivided and replaced by 
a series of smaller ones. The same variation has been observed 
among the Anthropoid Apes. This is an intensely interesting 
fact, as it approximates the molar of Man and the higher Apes 
with that of the multitubercular type, occurring among the 
oldest fossil and in the young of one of the two lowest living 
Mammals {e.g. Ornithorhynchus). Concerning the general question 
of mammalian tooth-genesis, choice to-day lies between the theory 
of " Trituberculism," originated by Elitimeyer and Cope, and 
staunchly upheld by the American Palaeontologists, and that of 
" Polybuny " or " Multituberculism " founded and recently de- 
veloped by Forsyth-Major. The advocates of the former would 
derive the various types of mammalian cheek-teeth from a 

^ Paper read before the Geological Society, London, 22nd May 1895. An 
admirable critical review of the subject of Fossil Man, by Dr. A. Keith, giving full 
references to original treatises up to the time of Newton's important work, will 
be found in Science Progress for July ] 895. 



PREFACE ix 

tricuspid prototype, by extension, subdivision, and superaddition 
of parts, and those of the latter from a multicuspid, by reduction, 
confluence, and suppression.^ Osborne has endeavoured to show ^ 
that the human molars may have been evolved out of a tri- 
tubercular -type. I would point out, on the other hand, that 
during the tooth changes of the human subject of to-day, there 
is indicated, on the part of the cheek-teeth, a progressive reduc- 
tion of that type of tooth represented by the first molar. The 
detailed facts concerning this process (cf. text, p. 160) appear to 
me to be more in accord with the theory of multituberculism ; 
and on this basis the suggestion arises whether the first molar may 
not stand in a similar relationship to the wisdom tooth of the 
multitubercular order as the deciduous molars do to it, the 
entire series of modifications being those of advancing reduction 
of a multitubercular type of tooth. 

No opportunity should be lost of excavating the Quaternary 
deposits of all parts of the world, especially where mixed with 
clays likely to be favourable to the preservation of human and 
other remains. Now that the African continent is being 
opened up, the scientific mind waits with longing for the 
careful investigation of its Tertiary Lacustrine deposits. Hugh 
Falconer long ago predicted that human remains would be 
forthcoming in the Tertiary deposits of India, and no one con- 
versant with recent work in Mammalian Palaeontology would 
doubt that the remains of ancestral Man must be sought thus 
far back in time. This prediction has been confirmed, by the 
discovery in 1894, by Noetling, in the Yenangyoung Oil -field, 
Burma, of flint flakes of early Pliocene date. I could desire 
no higher reward for the labour expended in placing this 
book before the English-speaking public than that it might 
help to awaken the interest necessary to ensure such investiga- 
tion. It may be added, as an appropriate comment, that the 
interest in Dwarf Eaces, recently revived through African ex- 
ploration and the fuller study of the natives of the Andaman 

^ For a fuller account of the history of these theories, and of the leading facts 
upon which they rest, cf. Osborne, Aineric. Naturalist^ vol. xxii. p. 1067 ; and 
Forsyth-Major, Proc, Zool. Soc., Lond., 1893, p. 196. 

'^ AtvU. AnzeigeVj Bd. vii. p. 740. Cf., however, the observations of Rose cited in 
this volume {infra, pp. 158 and 159). 



X THE STRUCTURE OF MAN 

Islands, has vastly increased, through the discovery that formerly 
dwarf races were widely distributed, evidence of their existence 
having been obtained in North Africa, Sicily, Switzerland, and 
the Pyrenees in the Old World, and in Central America in the 

New. 

In editing this work, I have spared no pains to bring it up 
to the standard of English requirements. In the course of the 
revision a free rendering, rather than a translation, of the original 
Grerman has been deemed in many places desirable ; and para- 
graphs dealing with incidental and controversial topics have 
been for the most part put into small type. Important altera- 
tions and intercalations are enclosed in square brackets, and 
for these I hold myself responsible. My friend Professor 
Arthur Thomson of Oxford has done me the great service of 
looking through the proof-sheets, and to him and my friends 
Dr. Forsyth-Major and Mr. Oldfield Thomas, I tender my sincere 
thanks for advice upon special topics. 

G. B. HOWES. 

Royal College op Science, London, 
South Kensington, S.W., 
May 1895. 



PREFACE TO THE SECOND, REVISED AND 
ENLARGED, GERMAN EDITION 

The book " Der Bau der Menschen " made its first appearance in 
the year 1887 in the form of an academic treatise, intended 
only for a limited circle of readers. There were no illustrations, 
and the method of treatment of the material was very brief, 
indeed, in many parts a mere sketch of the subject was given. 
Notwithstanding this, I received letters and questions which 
showed me that my treatise had awakened interest in a circle of 
readers wider than that for which it was originally intended, and 
I therefore decided to reissue it in a more complete form. 

The leading ideas are the same, although I think I may 
claim to have improved upon the manner and form in which 
they have been carried out. The large number of illustrations 
which accompany the text, as well as the wider foundation of 
comparative anatomy and ontogeny on which the subject rests, 
have, I hope, both made it more intelligible and greatly increased 
its usefulness. 

An index has been added, giving a review of the material 
dealt with, and also, for the use of the lay reader, a glossary of 
the zoological terms employed. 

I must express my hearty thanks to my publisher for the 
friendly assistance he has shown me. 

It is my earnest hope that this work in its new form may 
once more win recognition, since it aims at assisting man to 
know himself. 

THE AUTHOR 

Freiburg, I. Badex, 
May 1893. 



TABLE OF CONTENTS 



Preface .... 

Preface to the Second, Revised and Enlarged, German Edition- 
Table OF Contents . . . . 
List of Illustrations 
Introduction 
The Integument and the Tegumental Organs 

xlCiir • • . . • • . 

J^clIlS ....... 

Cutaneous Glands (Mammary Glands) 
The Skeleton — 

The Vertebral Column .... 

The Ribs and Sternum . • . . 

The Skull 

Skeleton of the Limbs .... 

The Pectoral (Shoulder) and Pelvic (Hip) Girdles 

The Skeleton of the Free Limbs 

The Skeleton of the Fore-Limb 

The Skeleton of the Hind-Limb 

Comparison of the Fore- and Hind-Limbs of Man 

Changes of Position of the Limbs in relation to the Trunk 
Muscular System ....... 

Retrogressive Muscles of the Trunk . 

The Muscles of the Cervical and Cephalic Regions 

Muscles of the Limbs . . . . 

Muscles which appear occasionally, and may be considered Atavistic 

Progressive Muscles 

Retrospect 
The Nervous System . 

The Spinal Cord 

Brain .... 



PAGE 
V 

xi 

• • • 

Xlll 

xvii 

1 

3 

3 

11 

12 

26 

36 

48 

67 

C8 

76 

77 

81 

91 

94 

97 

98 

102 

109 

112 

114 

120 

123 

123 

127 



XIV 



THE STRUCTURE OF MAN 



Peripheral Nervous System 
The Sympathetic System 

The Sense Organs 

Integumental Sense Organ 
The Olfactory Organ 
Jacobson's Organ . 
The Projectile Nose 
The Eye 
The Auditory Organ 

The Alimentary Canal and its Appendages 
Palatal Ridges 
Teeth . 
The Sublingua 
Thyroid and Thymus 
Bursa Pharyngea . 
CEsophagus and Stomach 
The Vermiform Process 
The Liver and Pancreas 

The Respiratory System 
The Larynx . 
The Lungs 

The Circulatory System 
The Heart . 
The Arterial System 
The Venous System 
The Spleen . 



Primitive Kidnej' 



The Urinogenital System 
The Pronephros and the 
Miillerian Duct 
Hymen . 
The Cloaca . 

External Genital Organs of the Female 
Male Genital Glands (Descensus Testiculorum) 
Suprarenal Bodies ..... 

Conspectus of the Organs mentioned in the Text, arranged on 
the Basis of their Physiological Condition 
Organs showing Retrogressive Characters ..... 
Organs showing Progressive Characters ..... 



PAGE 

138 
139 

140 
140 
141 

143 
147 
147 
150 

155 
155 
156 
161 
162 
164 
164 
167 
171 

171 
172 
175 

180 
180 
181 
184 
186 

187 
187 
189 
194 
194 
195 
196 
199 

200 
200 
204 



Ik 



CONTENTS XV 

PAGE 

List of the Organs and Topics considered in the Text, classed 

according to the systems to which they relate . .206 
Integument and Integumental Organs . . . . .206 

Skeletal System 206 

Muscular System ......... 207 

Nervous System ......... 208 

Sense Organs . . . . . . . . . . 208 

Alimentary System . . . . . . . .208 

Respiratory System ........ 208 

Circulatory System . . . . . . .209 

Urinogenital Apparatus ........ 209 

Some Organs and Vestiges op Organs which show Reversion to 

THE Condition of very Primitive Vertebrate Types . . 210 

Concluding Remarks . . . . . . . .212 

Glossary of Technical Zoological Terms occurring in the Text 219 
Index 223 



LIST OF ILLUSTRATIONS 

FIG. PAGE 

1. Face of an Embryo five months old, with the embryonic 

covering of hair. After A. Ecker ..... 4 

2. The Disposition of the Hair-Tracts on the Human Body. 

After Escbricht ......... 6 

3. The Vertex Coccygeus of the Human Embryo. After A. 

jjiCKer • • . . . .*. . . I 

4. FovEOLA CoccYGEA IN A HuMAN Embryo. After A. Ecker . 7 

5. And. Jeftichjeff, the " Russian Dog-man " .... 7 

6. A, Julia Pastrana. B, Hairy Aino, from the north-east 

coast of Yesso. After D. Macritchie ..... 8 

7. Young Orang-Utan, head from the side ..... 9 

8. Young Orang-Utan, head from the front . . . .10 

9. Diagrammatic Representations of the Early Develop- 

ment OF THE Leading Types of Mammary Glands. Modi- 
fied from Gegenbaur . . . . . .12 

10. Dissections of a Brooding Female of Echidna hystrix. 

A, Ventral aspect ; B, dorsal inner view . . .13 

11. The "Mammary Line" in the Pig's Embryo, at Different 

Stages. After 0. Schultze 15 

12. The Arrangement of the Teats in a Dog . .16 

13. Example of Polymasty. After D. Hansemann . . .19 

14. Case of Polymasty in a young Japanese Girl nineteen 

years old . . . . . . . .21 

15. Front view of the Body of a Hospital Assistant, twenty- 

two AND a half years OLD, fihowing teats and hair vortices. 
After 0. Ammon ........ 23 

16. Schreiner von Schonach, of the 16th Baden Infantry 

Regiment, showing supernumerary teats and teat areas. After 

0. Ammon ... ^ ..... 24 

17. Two Young Human Embryos, showing freely projecting tail . 27 

18. Tailed Human Embryo. After L. Gerlach . . . .28 



xviii THE STRUCTURE OF MAN 

no. PAGE 

19. " Tailed " Child, Moi, AGED twelve 29 

20. Diagrammatic Reconstruction op the Tail End op a 

Human Embryo, length of trunk 8 mm. After F. Keibel . 30 

20a. Diagrammatic Reconstruction op the Tail End op a 

Human Embryo, entire length 4 mm. After F. Keibel . 30 

21. The Pelvis, showing variations in sacrum, promontory, and 

associated parts ......... 36 

22. A, Transverse Section op the Thorax of a Lower Mammal 

(or op the Human Embryo) ; B, the Same op a Man . 36 

23. Diagrams op the Vertebral and Costal Skeleton. A, 

IN the Quadruped ; B, in Man 37 

24. Part of the Thoracic, and the whole Lumbar, Sacral, 

and Coccygeal Sections op a young Human Vertebral 
Column, dorsal aspect ....... 40 

25. Diagram of a Transverse Section of the Hip Girdle 

AND Sacrum : A, of a Salamander ; B, op "Mas, showing 
detailed constituents . . . . . . . .41 

26. A, First Thoracic Skeletal Segment, for comparison with 

B, Fifth Cervical Vertebra, of Man . . . .41 

27. A, Portion of the Thoracic Skeleton of an Adult Female 

possessed op a pair op free Cervical Ribs. B, Example 

OF THE reduction OF THE FIRST PAIR OP THORACIC RiBS, 

IN AN Adult Male 42 

28. Shoulder Girdle of Ornithorhynchus . . . .46 

29. Episternum of an Embryo Mole. After A. Gdtte . . 47 

30. Episternal Vestiges in Man .48 

31. A, Slightly Diagrammatic Median Longitudinal Section 

through the Head and Anterior Portion of the Trunk 
OF A Human Embryo, seventeen to eighteen weeks old. 
After W. His. B, Embryo Torpedo, as seen by transmitted 
light. After H. E. and F. Ziegler 49 

32. Skull of Immanuel Kant. After C. von Kupffer . . 60 

33. Skull of a Child seven years old . . . . .51 

34. Skull of an Australian from the Murray River . . 51 

35. Skull of a young Orang-Utan .52 

36. Skull of an Adult Orang-Utan . . . . .52 

37. Median Sections through the Head of a Deer, a Baboon, 

and a Man ......... 54 

38. A to C, Various Forms of the os Incae. D, E, Diagrams 

OP the Bones op the Occipital Region in the Embryo. 
Partly after Ficalbi . . . . . . .56 



LIST OF ILLUSTRATIONS xix 

FIO. PAGE 

39. Skull of a Girl two years old, showing broad ala magna of 

sphenoid .......... 59 

40. Skull op an Aboriginal Australian, showing contracted 

ala magna of the sphenoid . . . . . . .59 

41. Skull of a Negro Eunuch, showing epipteric bone . . 61 

42. Skull of a Turco, with the temporal bone nearly reaching 

the frontal .......... 62 

43. Skull of a two-year-old Chimpanzee, from the side . . 62 

44. Hard Palate of a Caucasian, a Negro, and an Adult 

Orang-Utan 63 

45. Head of a Human Embryo of the Fourth Month, to show 

the auditory ossicles, tympanic ring, with Meckel's cartilage, 

and the hyoid and thyroid apparatus . . . . .65 

46. Skull of a Tailed Amphibian (Menovoma) . . . .66 

47. Transverse Section through the Embryo of a Shark 

{Pristiwnis melanostomttsjj showing limb buds . . .67 

48. Diagram illustrating the Development of the Fins of 

A Fish 68 

49. Diagrammatic Representation of three successive Stages 

IN THE Development of the Pelvic Fins of a Shark . 69 

50. An Attempt to depict diagrammatic ally the Process by 

which the Limbs of Terrestrial Vertebrates would 
appear to have been probably derived from the fins 
OF Fishes .70 

51. Pectoral Girdle of a Tailed Amphibian, ventral aspect . 71 

52. Right Blade-Bone of a New-born Child, showing ossifica- 

tion of the coracoid . . . . . . . .72 

53. Pelvis of a Female Chimpanzee, two years old . . 75 

54. Right Humerus of a Negro, showing perforation of the 

olecranon fossa . . . . . . . . .77 

55. Distal Extremity of the Humerus, to show epicondylar 

foramina, in Hatteria, Lacerta, the Cat, and in Man . . 78 

56. Skeleton of the Hind -Limb of a Tailed Amphibian 

{Spelerpes fuscus) . . . . . . . .79 

57. Diagrams of the Human Carpus. A, Embryo ; B, Adult . 80 

58. Proximal half of a left Human Femur possessed of three 

Trochanters 82 

59. The Ankle- Joint, in a Chimpanzee, an Australian native, and 

a Caucasian ......... 84 

60. Skeleton of the left Pes of a Chimpanzee, dorsal aspect 85 

61. Skeleton of the Left Hand, dorsal aspect .... 86 

62. Skeleton of the Left Foot, dorsal aspect . . . .87 



XX THE STRUCTURE OF MAN 

FIO. PAGE 

63. Fore- and Hind-Limbs of a two months' Human Embryo, 

to show the position of the thumb and great toe . . . 89 

64. Posterior End of the Body of two Human Embryos, with left 

hind-limb and umbilical cord ...... 90 

65. Larval Salamander. After Hatschek. A, with limbs turned 

down ; B, with limbs turned up . . . . . .92 

66. Skeleton of a Young Bear, illustrating the positions of the 

limbs. After Hatschek . . . . . . 93 

67. Diagram of the Distribution of the Platysma over the 

Head. After Gegenbaur . . . . . . .104 

68. Superficial Musculature of the Face in Lepilemur musU- 

linus. After Ruge . . . . . .105 

69. Facial Muscles and Nerves of the Lemuroid PropUhecus. 

After Ruge ......... 106 

70. Muscles of the Epicranial Region in Man, with certain of 

THE Facial Muscles. After Gegenbaur . . . .107 

71. The Pinna, in Man, a Baboon, an Ox, Macacus and Cerco- 

pithecus. After Schwalbe and Henle . . . . .108 

72. Superficial Muscles and Tendons of the Dorsum of the 

Foot. After Rauber Ill 

73. Deep Muscles of the Flexor Side of the Forearm. After 

Rauber . . . . . . . . . .116 

74. Median Plantar Muscles in their connection with the 

Flexor Tendons. After Rauber. 117 

75. Deep Dorsal Muscles of the Forearm. After Rauber . .118 

76. Lower Portion of the Spinal Cord, with the Cauda Equina 

AND THE Dura Mater, dorsal aspect. After Schwalbe . . 124 

77. Brain of a Dog-fish {Sayllum canicula), three views . .126 

78. Cerebrum of a Female Chimpanzee two years old, showing 

asymmetrical development . . . . . . .128 

79. Brain of a Female Chimpanzee two years old, lateral aspect 128 

80. Cerebrum of the Gibbon {Hylohates), lateral aspect . . .129 

81. Cerebrum of a seven to eight months* Human Embryo, 

dorsal aspect . . . . . . .129 

82. Cerebrum of a seven to eight months' Human Embryo, 

lateral aspect . . . . . . . . .130 

83. Hypothetical Median-Longitudinal Section through the 

Skull and Brain of a Vertebrate Embryo. Partly after 
Huxley . . . . . . .131 

84. Brain of a Rabbit, three views 132 

85. Longitudinal Section through the Pineal Organ of a 

"Reptile {Hatteria punctata). After Baldwin Spencer . .133 



LIST OF ILLUSTRATIONS 



FIO. 

86. 

87. 
88. 

89. 



XXI 

PAGE 



90. 

91. 
92. 



93. 
94. 

95. 
96. 
97. 

98. 
99. 

100. 
101. 
102. 
103. 



104. 



105. 



Median Longitudinal Section through the Head op a 

Newly-hatched Larva op the Lamprey (Petromyzon plarteri) 136 
Lateral View op the Nasal Chamber op a Human Embryo . 141 

Sagittal Section through the Nasal and Buccal Cavities 
OF THE Human Head 142 

A-D, Stages in the Development op the so-called Jacobson's 
Organ op the Urodela. E, the same Organ in a Gymno- 
PHioNE. F-H, The Nose and Jacobson's Organ in 
Lacerta, a Placental Mammal, and Ornithorhynchus, H, 
after Symington . ....... 144-145 

Heads of two Human Embryos at second and third months 147 

Human Eye . 148 

Diagram to illustrate the Shifting op the Lachrymal 
Gland, which has taken place in the course op 

Phylogeny . . .149 

Eye op a Mongolian, with the Epicanthus . . . .150 

Diagram to illustrate the Metamorphosis during Develop- 
ment OP the Visceral Skeletal Arches . . . .151 

Palate op a Human Embryo at the eighth month . .155 

Palatal Folds op the Racoon (Procyon lotor), . . .156 

Human Mouth, in which the Development op the Upper 
Outer Incisors has been Suppressed . . . .158 

Human Stomach . 166 

The C^cum and Processus Vermipormis in a Human 
Embryo 167 

The CiECUM and Vermiform Process op a Human Embryo . 168 

The CiECUM and A^ermiporm Process in a Kangaroo . .169 

Human Larynx IN Frontal Section 174 

A Series op wholly Diagrammatic Figures to illustrate 
THE Comparative Morphology of the Urinogenital 
Organs of the Vertebrata 191 

Diagrammatic Representations of the Chief Types of 
Uterus occurring in the Placental Mammals . . .193 

A, Partly Diagrammatic Representation of the Embryonic 
Urinogenital Apparatus op a Male Mammal, showing its 
relations to the Ventral abdominal wall. B, The Penis and 
Scrotum op a Human Embryo, 15 cm. long. Both figures 
founded on the work of Klaatsch . .197 



THE STKUCTUKE OF MAN 



INTEODUCTIOlSr 

Some thirty-four years have elapsed since the publication of 
Charles Darwin's work On the Origin of Species hy Means of 
Natural Selection. A short period of time, and yet important 
enough to throw into the shade all previous centuries, so profound 
is the significance of the results obtained in it, in the field of 
Natural Science. 

Darwin's book brought about a reformation not only of 
Zoology, but of our whole knowledge of surrounding Nature. It 
marked, in fact, the commencement of a new epoch, and of a new 
cosmology. This has been said so often and demonstrated so 
thoroughly, that the topic need not be further enlarged upon 
here. I cannot, however, refrain from briefly sketching the 
condition of the natural sciences during the last two centuries, 
since it is only on such a background that a correct picture of 
the enormous transformation which has since been effected in the 
intellectual life of all cultured nations can be obtaine(i 

In spite of the great discoveries made, in the sixteenth and 
seventeenth centuries, by such men as Kepler, Newton, Harvey, 
Schwammerdam, Malpighi, and Leeuwenhoeck, the Aristotelian 
philosophy, which had been stirred to new life at the period of the 
Keformation, was universally accepted. Its exegetical principle 
rested on the assumption of the existence of an intelligent design, 
to which the phenomena of nature were subordinated. The 
teleological speculations which arose out of it, and the resulting 
anthropocentric and anthropomorphic cosmology, outlived the 
centuries named. Indeed, in spite of all progress in science, they 
continued to count many of their most brilliant advocates among 
distinguished scientific men, even into the fifties of the present 
centurj^ This philosophy was deeply rooted in human vanity, 

B 



2 THE STRUCTURE OF MAN 

receiving immense support from the Mosaic cosmogony, which 
assigned to Man a sovereign position over nature, and especially 
over the animal kingdom. Every attempt to shake this sover- 
eignty was regarded as heresy. Even the laity persistently 
refused to submit Man to the same strict scientific analysis 
which, with increasing clearness, was being applied to the 
surrounding forms of life by the existing schools of natural 
philosophy. 

In spite of this opposition, however, the theory of descent 
steadily gained ground, and its advance was especially favoured 
by new and surprising results attained in the three closely 
allied branches of science — Palaeontology, Comparative Anatomy, 
and Embryology. The proofs of the great changes which must have 
taken place in both the animal and vegetable kingdoms, during 
the immeasurable periods consumed in the development of our 
planet, became more and more convincing. 

The earlier assumption of repeated separate acts of creation 
gave way to a more satisfactory and strictly scientific conception 
of the fundamental unity of all organic nature. " Blood relation- 
ship, and not some unknown plan of creation, forms the invisible 
band which unites organisms in various degrees of similarity," 
and in this great family Man must find his place. He forms 
but a link in the chain, and has no right to consider himself an 
exception. To claim for himself a special act of creation, in order 
to account for his appearance in the series of living creatures, would 
be nothing less than a denial of the unity of physiological science. 

It may be that we have not as yet succeeded in tracing back 
the primitive history of Man beyond diluvial times by the light 
of palaeontological discoveries, for no certain proof of the actual 
existence of tertiary Man has been obtained. But this '^ break 
in the record " cannot in the least impair the evidence of mor- 
phology as to the real ancestry of Man. Comparative morpho- 
logy points not only to the essentially similar plan of organisa- 
tion of the bodies of all Vertebrates, and to the agreement in 
their entrance into life, individual existence, and final dissolution, 
but also to the occurrence in them of certain organs, or parts of 
organs, now known as " vestigial." 

By such organs are meant those which were formerly of greater 
physiological significance than at present. In the course of 
generations, in consequence of the adaptation of the body to special 
conditions of life, they have been, so to speak, put out of the 
running, subjected to reduction or degeneration, and now persist as 



INTRODUCTION 3 

mere vestiges. Such organs, which remain inexplicable by the 
doctrine of special creation or upon any teleological hypothesis, can 
be satisfactorily explained by the theory of selection. They are 
found alike in the lower animals and in Man ; and it is evident 
that these relics of a long vanished epoch are of peculiar interest in 
this latter case, where Palaeontology offers us no help. Their closer 
study, therefore, has a fascination for us which we cannot resist. 

In the attempt to track the primitive Man, i.e. to follow up 
the traces of Man's ancestry, we shall find indications — here of 
progression — there of retrogression. These will help to throw 
light on Man's position among the Vertebrata. 

Thirty-one years have passed since Huxley published his 
Evidence as to Maris Place in Nature. When we remember 
how much work has been done since, and what results have been 
attained in physical Anthropology, Anatomy, and Embryology, 
it will, I think, be evident that the time has come once more to 
look back, to gather together into a whole the new material which 
now lies scattered far and wide, and from it to attempt once more 
to estimate what Man is, what he was, and what he may become. 



THE INTEGUMENT AND THE TEGUMENTAL OEGANS 

In Man, as in all Vertebrata, two of the three germinal 
layers take part in the formation of the integument, the outer 
(ectoderm) and the middle (mesoderm). The ectoderm gives rise 
to the epidermis (cuticle or scarf-skin) and the mesoderm to the 
corium or dermis. 

The epidermis, again, consists of a superficial and a deep layer, 
of which the latter is of the greater physiological importance, all 
the so-called cutaneous or tegumental organs owing their origin 
to it. To these belong (1) the various corneous structures, such 
as hair and nails ; (2) many different kinds of glands ; and (3) 
the terminal apparatus of nearly all the sensory organs. 

Hair 

Man is the least hairy of all the Primates ; indeed, his skin 
may be called almost smooth. Apart from the head, the only 
parts of the body abundantly supplied with hair are, as a rule, 
the pubic, perineal, and axillary regions, although a careful 
examination of the skin shows that hair follicles are to be found 
over its whole surface. In males, in addition to the parts already 



4 THE STRUCTURE OF MAN 

mentiooed, hair ie frequently strongly developed on the ventral 
and dorsal regions of the trunk, i e on the breast and abdomeii, 
and on the buttocks and neck, and on the limbs. 

These facta alone would suffice to render it probable that 
man was in primitive times far more haiij than at present, but 
still stronger evidence can be biought foiward. 



->>., 





Tw. ].— Face o 

The first traces of hair appear, in the human embryo, as early 
as the twelfth or thirteenth week, the earliest being foiind about 
the forehead, the mouth, and the eyebrows, i.e. in those parts of 
the body where, in the lower Mammals, the so-called " whiskers " 
(vibrissEe) or tactile haii-s usually appear. It is evident that, 
morphologically, the hairs about the jiiouth and eyebrows in Mea 
belong to tliis same categorj'. The hairs begin to break through 
the integimient at the end of the fifth month, and they con- 
tinue to do so till the seventh month, those of the head being the 
earliest and tliose of the limbs the latest to appear.^ In the 

' The fact of the apiwaranoa of hair in different parta of the liody in regular 
order, the lower limbs being the lost to beuonie thns clothed, lias apparently attained 
popular recognition in the very old proverb "lie haa bair on his toes."' which may 
doubtless be referred t« a time when boots and aboas did nut phiy the part they now 
do. From what I liave gathered in conversation n'itli inhabitants of Berne (Obec- 



TEGUMENTAL ORGANS 5 

sixth month, the whole body of the embryo, except the surface 
of the hands and feet, the red edges of the lips, the glans penis 
and* clitoridis, and the inner surface of the foreskin, is covered 
with abundant soft woolly hair (lanugo).^ 

In certain parts of the body the hairs are arranged closely 
and quite regularly in tracts, just as birds' feathers are arranged 
in the so-called '' jpterylce" These hair- tracts (Fig. 2) are vortex- 
like in arrangement, diverging over some areas, converging over 
others. 

In the former (cf. the hair of the head) the hairs point with 
their free ends outwards, from the vertex as a centre ; in the latter, 
on the other hand, the direction of the hairs is the reverse of this, 
their free ends being directed inwards, i.e. towards the centre of 
the vortex. This latter, converging, disposition is only found, both 
in the lower Mammals and in Man, at parts where an organ either 
projects during life, as in the case of horns and antlers, or has pro- 
jected at some period in ontogenetic or phylogenetic development. 

An excellent example of this is afforded by the radial 
arrangement of hairs often found in the male sex in the region 
of the navel, or still better by the " vertex coccygeus " (Fig. 3) 
described by Ecker. The position of this latter exactly corre- 
sponds in the embryo with the point at which, before the bending 
of the OS sacrum took place, the extremity of the coccyx pushed 
against the skin ; i.e. with the point where the coccyx formerly 
projected as a free tail, the cauda humana (cf pp. 27, 28). 

Just before birth the position of the vertex coccygeus shifts, 
a hairless area being developed (Glabella coccygea) which may 
sink in to form a pit (Foveola coccygea, /y. Fig. 4) (Ecker). On 
the other hand it frequently attains such a degree of development, 

deutschen) and of Holland (Niederdeutschen), I am convinced that **on his toes" 
(Zehen) is the right version of the proverb, and not **on his teeth " (Zahnen). 

Many similar perversions of old popular sayings, or of words of which the original 
meaning has gradually been lost in later generations, are to be found ; for instance, 
the expression " to have his sheep (Schaffchen) in the dry " originated on the coast, 
where "to have his ship (Schiffchen) in the dry" is still heard. Again, the 
Schonberg near Freiburg was originally called Schynberg, from Schyn, which means 
a witch, a word which has been retained in the " Witch's Valley " at the foot of this 
hill, and in the Swabian term of contempt ** Schyn- Aas " (literally witch carcase). 

* In the fourth or fifth month the human embryo has a distinct stratum comeum 
with an epidermal layer outside it, which corresponds with the epitrichium of Rep- 
tiles and of many Mammalian embryos (Edentata, DicotyleSf Sus^ and others). After 
the sixth month of embryonic life the latter disappears from most parts of the body. 
The epitrichial layer covers the hairs and the glands, being able to some extent to 
keep back the secretions of the latter. In this way it provides for the accumulation 
of a rich secretory deposit, the so-called "vernix caseosa." 



THE STRUCTURE OF MAN 



even in the sistb or seventh month, that the hair may be twirled 
betweeQ the fingers like a moustache. 



'.^ 




TEGUMENTAL ORGANS 
Hypertrichosis, or excessive hairiness, which also nob : 





Fia. 5.— And. Jeftichjeff, the " Russian 



frequently occurs in adults of both sexes, is a very interesting 
phenomenon. By far the greater number of such cases, as 



TEGUMENTAL ORGANS 



Ecker has specially pointed out, appear to be due to a temporary 
arrest in the development of the hairy covering, and the persistence 
and subsequent growth in post-embryonic life of the fcetal woolly 
covering or lanugo. We can describe this as Pseudohj-pertrichosia I 
lanuginosa (Bonnet), since normally tlie greater part of the lanugo 
is said to be shed, and to be replaced by stronger medullated 
hairs. 




To this category belong all the well-known cases of " Dog- 
men," or hairy men,^ e.g. the Ambraser hairy family, Barbara 
TJslerin, and Mrs. I^nt (commonly known as Zennora Pastrana 
II.) ; also the Russian Dog-man Jeftiehjeff (Fig. 5), his son Fedor, 
and the Burmese Shwe-Maong and his family. In the cases of 
Jeftiehjeff senior, and Shw^-Maong, the whole face, except the 
red edges of the lips, was thickly covered with delicate, soft, 
and partly curly hair, such as also projected from the orifices 
of the ears and nose. The body of the Eussiau was somewhat 

> In these cases defects in the dentition and otlier traces of arrested dcTelopment 
{e.g. retarded pabertj) not infrcqaentl; occur. 



10 



THE STRUCTURE OF MAN 



less hairy than that of the Burmese, the whole of whose trunk 
and limha was covered with hair from 4-8 inches long. 

The extreme hairiness of the Ainos (Fig. 6, B) may probably 
also be referred to Pseudohypertrichosis ; but this point requires 
closer investigation. 

In all the cases mentioned above, the persistence of the 
vestigial lanugo must imdoubtedly be regarded as a return to a 




i'JppiW^'l^ 



primitive hairy condition in Man ; whereas true hairiness, or 
" hypertrichosis vera," is quite a different thing. This, which 
was well exemplified in the once famous dancer Julia Pastrana I., 
is due to an excessive development of the secondary covering of 
hair. In her case (Pig- 6, A) the greater part of the primary 
hairy covering (the lanugo) must be considered to have been shed 
during embryonic development. 

Bonnet rightly points out that " in Man and the domestic 
animals, the accessory structures of the epidermis accurately 
register the balance of nutrition," and that various circumstances. 



TEGUMENTAL ORGANS 11 

such as climate, domestication, natm-al and artificial selection, 
influence the hairy covering. Further, the development of this 
may be in inverse ratio to the thickness of the integument, and 
particularly of the epidermis (Leydig), the hair and the epidermis 
supplementing one another in the work of protecting the body. 
This is illustrated, on the one hand, by animals which have a 
delicate epidermis and thin skin and a thick covering of wool or 
fur ; and on the other by animals like the Ehinoceroses, Hippo- 
potami, some Armadillos, and Scaly Ant-Eaters, in which, while 
the epidermis is so thickened as to form a hard carapace, the 
hair is very scanty. 

I cannot leave this subject without touching upon the question of the 
origin of the Mammalia, especially as this chapter in morphology has recently 
been ably dealt with by Max Weber, who deduces reasons for taking up the 
following position. The first Mammals, as descendants from primitive scaly 
Reptiles, were covered with scales, differing from those of the Reptiles only in 
minor points. Behind the scales of the primitive Mammals there first 
appeared a few small hairs, the origin of which it is difficult to explain with 
certainty. By degrees, as a constant temperature was maintained by the 
body, the covering of hair attained a g;reater development and the scales 
degenerated. Scales, somewhat specialised, are still retained as a covering 
for the mammalian body in a few cases, e.g. Armadillos and Scaly Ant-Eaters. 
Among other Mammals they are found, as a rule, only on the tail and limbs. 
The recurrent arrangement of the hairs, however, due to their original 
development behind scales, has very generally persisted, and on this basis 
hairs may be considered to imply the earlier presence of scales. 

Nails 

The nails of the fourth and fifth fingers (and especially the 
latter) most nearly suggest the claws of the lower animals, in being 
decidedly arched from side to side. As the th\mib is approached 
the nails become more and more flat, and the like is true of the 
great toe as compared with the four lesser toes. This condition 
commences with the Lemuroidea [although among the lower 
Mammalia the Squirrels, for example, bear a flattened nail upon 
the pollex]. 

On the under edge of the nail, between it and the ball of the 
finger, is found the last vestige of a structure which in the Apes 
is covered with a thickened layer of epidermis.^ This structure 
undergoes considerable degeneration, even during intra -uterine 
life, through the advancing development of the ball of the finger 
(Gegenbaur). 

* This stnictiu-e is most conspicuous in the Ungiilata, and it is there kno^vn as the 
"frog." 



THE STRUCTURE OF MAN 



Cutaneous Glands (Mammaky Glands) 

The cutaneous glands of Man fall into two classes : sweat- 
glands and sebaceous glands, with their modifications. 

Certain of these glands play an important part in Mammals 
on account of their odoriferous secretions. In Man the secretion 
of the axillary and anal glands is well known to have a penetrating 
odour, but the significance of this we have so far failed to discover. 




FlQ. 9. — DlAORAUUATlC REPRESENTATIONS OF TBE EaBLT DeVELOFUENT OF THB 

Lbadinq Tipks oy Mahmart Glakds, (Modified from G^onbanr.) 
A, Ficat or undifferentiated (niamniBr; pit) stage ; B, stage of the false test ; C, stags 
of the true teat ; v. n., rim (or rampart) of the glandular u-ea ; f.ff. , glandular areft ; 
gl., mammary glands; d., mammary onnal. 

The mammary glands, in all Mammals higher than the Mono- 
tremata,' must be regarded as aggregates of much modified sebace- 
ous glands. This is attested not only by their whole structure, 
and by the nature of their secretion, but also by the fact that the 
sebaceous glands lying immediately around the teat in the female, 
the so-called Montgomery's glands, grow larger when lactation 
begins, many of them yielding milk. This functional transition 
from sebaceous to mammary glands furnishes the best evidence for 
their homology (Gegenbaur). In rare cases sebaceous glands stiU 
farther from the teat may also take part in lactation, instances being 
known in which such glands extended as far as the axillary region. 

These facts lead us to believe, d. priori, that all parts of the 
skin may be capable of producing mammary glanda 

' The mammary organ of the MoDOtremata is derived from sireat-glancls, so that w« 
have a diphyletic origin for the maimnary glands collectively considered (Oegenbanr). 



TEGUMENTAL ORGANS 13 

The development of mammary glands and teats is always 
initiated by a shallow depression of the integument {f.g.. Fig. 9, A), 
the mammary pit ; the base of this pit is the glandular area, 
and the surroimding border (v) the rampart of the gland. The 
Malpighian stratum of the epidermis at the base of the glandular 
area, by inward proliferation, gives i-ise to the glandular tissue. 

The mode of development of the teats is not the same for all 




A Bboodiho Fkmale of Echidna kystrlx. 

iev. 1 1. 1'he two tutls of hair, in the lateral folds of 
the mammary poucli from which the secretion flows. On each side of the poach 
(6.?«,), vihich is snrronnded by strong muscles, a gronp of niammiiry glands (jf.m.) 
opens ; d. denotes the cloaca in each figure. (After W. Haauke.) 

Mammals. Either (Fig. 9, B) the rampart which borders the 
depression rises and forms a tube (the lumen of which is known 
as the mammary canal), into the base of which the true ducts 
open, or (Fig. 9, C) the glandular area rises in the shape of a 
papilla, while the rampart degenerates. The latter, in which the 
nipple must be considered as a secondarj' formation, is exemplified 
in the Marsupials, the Lemuroidea, Apes, and Man ; in the former, 
which obtains in the Carnivorar Pigs, Horses, and Ruminants, it 
is a primary formation. The first indications of the primarj' 



14 THE STRUCTURE OF MAN 

formation are found in certain Marsupials {Phalangista vvlpina) 
and among placental Mammals as high as Carnivora (Gegenbaur). 

The question now arises, whether the developmental stages 
of the mammary glands point to primitive conditions which in 
any degree persist in the lower Mammals ? An examination of 
the Monotremata shows that this may be the case ; and to make 
this clear we must enter somewhat further into detail 

In the Monotremata, in which as yet there are no teats, the 
ducts of the mammary organ open in a group on the ventral 
integument. As the reproductive period approaches, if fertilisation 
has taken place, a temporary depression of the ventral integument 
occurs, which gives rise to a pouch (&.m., Fig. 10). The egg is 
deposited in this pouch, and the mammary fluid is probably 
carried to the young animal to which the egg gives rise, by 
means of the pointed tufts of hair which project around the 
apertures of the glands. Closer examination shows that the ducts 
open into two cutaneous depressions, which lie near the tufts just 
mentioned, in the lateral folds of the mammary pouch. These 
may be called mammary pits, and are of considerable importance, 
because they are repeated in the development of the various 
forms of nipples and mammary organs occurring in the higher 
orders of Mammals. We have here a glandular area which, like 
that already described (Fig 9, A), is nothing more than a de- 
pressed portion of the external integument, with all its charactier- 
istic derivatives, such as hairs, glands, and pigment. 

Before passing to the question of the disposition of the 
mammary glands on the body, an important discovery, for which ' 
we have to thank Oskar Schultze, must be mentioned. 

In young embryos of Mammals, e.g. the Pig, a ridge-like 
prominence (/.r/i., Fig. 11) is found on each side, running from the 
base of the anterior limb, which is at this period a mere stump, 
towards that of the posterior limb and into the inguinal furrow. 
This is due to a linear thickening of the developing epidermis, 
and especially of the stratum Malpighi. This lateral epidermal 
ridge represents the common epithelial rudiment of the mammary 
glands, and may be called the " Mammary Line." Along this line 
a row of fusiform thickenings develop (Fig. 1 1, B and C), the whole 
presenting the appearance of a regularly varicose fibre. These 
protruding " primitive teats " flatten out again at a later stage, 
and in no way represent the teats which form later, although they 
generally correspond in number with the centres of origin of the 
future glands. 




Fio. 11. — Tbe "Mammary Lim" {l.m.) im the Pio'b Embryo at Diffi 
STAOEa. (After 0. Schultze.) 
A, embryo I, 5 cm. (Croia bend to coccyi) ; B, embryo I, 7 cm. long ; 
C, embryo I, 9 cm. long. 



16 



THE STRUCTURE OF MAN 



Eesorption of those portions of the mammary line which lie 
between the primitive teats soon begins to take place, and in such 
a manner that the originally elongated and fusiform eminences 
become roimded. At a later stage, as above stated, these fatten 
out, and extend at the same time into the subjacent tissues. 
In this way they form the well-known button -like epidermal 
proliferations, which have generally been considered to mark the 

first stage in the develop- 
ment of the mammary 
glands, a stage which is 
immediately followed by 
,the formation of the so- 
called mammary pits. 

Later on we shall have 
to refer to the conclusions, 
with respect to Man, to 
be drawn from Schultze's 
observation, but we may 
now turn to the ques- 
tion of the disposition of 
the mammary glands on 
the body. 

Although the position 
of these organs may vary 
greatly, the ventral side of 
the body has the prefer- 
ence on account of the 
greater facility with which 
the young can reach the teats. The position in the postero- 
ventral region, i.e. in the region of the groin, may be considered 
the most primitive. The udder of some Ungulates, as is well 
known, is found in this position, and the same is also the case 
in the Cetacea. In the great group of the Carnivora, and in 
the Pigs, the teats are found on the thoracic and abdominal 
regions (Fig. 12), arranged in two rows converging towards the 
pelvic region. In other groups, again, they are confined to the 
pectoral region (e.g. Elephants, Sirenia, many Lemuroidea, Chirop- 
tera. Apes, and Man). 

The great range of variation in the position of the teats and 
mammary glands deserves careful attention, since it enables us to 
satisfactorily explain the existence of so-called supernumerary 
mammary glands and teats, which often occur in human beings 




Fig. 12. — Showing the Arrangement of the 
Teats in a Dog, in two longitudinal rows con- 
verging towards the pelvic region.) 



TEGUMENTAL ORGANS 17 

of both sexes. The term polymasty is used to denote the former 
condition, and polythely ^ the latter. 

During the last three decades an immense number of cases 
of this kind have been recorded ; and as it is quite impossible to 
consider them all here, we must limit ourselves to a few of the 
more characteristic. We may remark at the outset that the 
increase in number of the mammary glands or teats, in both men 
and women, may be regarded as a return to a primitive condition 
in which many glands were developed and many yoimg were 
produced at a birth. The change from polymasty to bimasty 
can be observed at the present day in the Lemuroidea. In these 
animals the teats of the groin and abdomen are functionless and 
clearly degenerating, whereas the pair which occur in the pectoral 
region are well developed. In accordance with this most 
Lemuroids give birth to only two young, which they carry about 
at the breast. This habit permits of the greatest freedom of 
movement (for example in climbing), and renders explicable the 
gradual degeneration of the other teats. 

But how are we to explain the presence of such pronounced 
vestigial organs as the teats of the male human being ? 

It is usually considered that they are inherited from the 
female, and it is possible that this explanation is correct. But 
when we find that in the Monotremata the mammary glands are 
almost equally well developed in both the male and the female, 
it seems not improbable that originally both sexes may have 
taken an equal share in the bringing up of the young. 

It is certain that a functional condition of the mammary 
glands (gynsekomasty) may occur in men.^ [Humboldt records 
a case, to which he bore ocular testimony, of a man who, at the 
age of thirty-two, was left in charge of a sucking child by the 
death of his wife. Not knowing how to rear it, he in despair 
pressed it to his own bosom ; and it is alleged that hypertrophy 
of his breast, with milk secretion sufficient for the rearing of the 
infant, was thereby induced.]^ It is also known that boys, both 

^ Either well-developed or rudimentary supernumerary teats are not infrequently 
found in various Mammalian orders, for instance two rudimentary teats often occur 
behind the four normal teats of the cow. 

* [I can testify to this in person, for, while bathing with friends on the Welsh 
coast at the age of thirty-six years, milk, suflScient to cover a threepennypiece, issued 
from my left breast on contact with the towel. This state of affairs continued for 
three days, the right breast remaining inactive. — G. B. H.] 

' [During the passage of these pages through the press this subject has been 
comprehensively dealt with by Schaumann {Verhandlg, d. physik. -medic, Oeaellsch.^ 
Wiirzburg, Bd. xxviii. p. 1)]. 

C 



18 THE STRUCTURE OF MAN 

soon after birth and at the time of puberty, may produce milk 
(so-called " witch's milk ") from more or less swollen breasts.^ 
Milk has also certainly been obtained from male goats and from 
castrated rams, and this has been found on chemical analysis to 
be even richer in caseine than ordinary milk. 

[In this connection it is interesting to note that Dobson has 
called attention (British Museum Catalogue of the Chiroptera, 
Lond., 1878, pp. 79 and 83) to the great development of the 
teats in the males of certain frugivorous Bats. He points out 
that while many Bats are known to bring forth two young at a 
birth, he has never found a mother with more than one clinging 
to her body ; and he inclines to the belief that in such cases the 
male may relieve the female of the charge of one of the young 
ones (as the weight of two might render flight difficult or 
impossible). He suggests that " instances of the male performing 
the office of nurse are probably not uncommon among Bats."] 

The following results on the subject of supernimierary breasts 
and teats were obtained by Leichtenstern, from the study of 
extensive data : — 

Cases of polythely, with or without polymasty, were observed 
with almost equal frequency in the two sexes. On an average, 
one case may be expected in every 500 individuals. 

In 9 1 per cent the accessory glands and teats were developed 
on the anterior side of the thorax, and in by far the greater 
number (94 per cent of these) they were found below (caudad of) 
the normal teats, in a convergent disposition. 

The following is a table showing the position occupied by 
the accessory mammillae in the 105 cases recorded by Leichten- 
stern : — 



On the anterior side of the thorax 


96 cases 


In the axilla 


5 „ 


On the back 


2 „ 


Above the acromion . 


1 case 


On the outer side of the hip . 


1 „ 



Eudimentary breasts occurring above (cephalad of) the normal 
ones are of rare occurrence (3 per cent), and these (Fig. 13, m") 
always lie outside the normal mammary line in the direction 
of the axilla. Want of symmetry, especially on the left side, is 
common in all cases of rudimentary teats or mammary areas, in 
whatever part of the body they occur. The rarest condition 

^ Decided swelling of the breasts is sometimes found in youths of from twenty to 
twenty-one years of age, in cases of retarded puberty (Ammon). 



TEGUMENTAL ORGANS 



19 



(only one case being known) is that in which a supernumerary 
teat occurs in the same horizontal plane with the normal teats, 
either at or near the median line. 

Hyrtl put forward the view that the greater development of 
the left breast is due to the habit of feeding the child from that, 
in order to leave the right arm free. Leichtenstern opposes this, 
but does not furnish any satisfactory explanation of the fact.^ 




Fig. 13. — Example of Polymastt. (After Hansemann. } 

The position of the supernumerary breast {m") is superior and lateral to that of 
the normal (m'). The left accessory gland has a second teat (m'"). 

Eudimentary mammary organs were never found by Leichten- 
stern below the costal ridge or in the inguinal region. 

In the Dog the normal nimiber of teats varies from seven to 
ten, and Cuvier's dictimi that the numerical variation in breasts 
is greatest where they are most nmnerous is thus confirmed. 

Towards the end of the last century. Professor Socin of Basel, 
and subsequently the Medical Faculty of the University of 
Tubingen, were consulted by a lady with four breasts, as to 
whether she could marry without incurring the danger of having 
twins at every birth. The authorities decided that polymasty 
did not imply predisposition to bear twins, and the result proved 
the correctness of this opinion. Among seventy women with 
polymasty, twins are known to have been born in only three cases. 

* [It may be remarked here that the young ** vervet " {CercopUhecus lalaiidii) has 
been recently observed to suck both teats at once (Proc. Zool, Soc, Lond. 1893, 
p. 615).] 



20 THE STRUCTURE OF MAN 

If the supernumerary teat is sufficiently large, it can be used 
for suckling ; but it is generally too small for this purpose, and 
is merely an encimibrance, since when the child is being fed 
from the normal breast, milk may dribble from the accessory one. 

Hansemann has recorded the case of a married sempstress, 
forty-five years old (Fig. 13), who had, above and laterally to 
the normal breasts, two accessory ones, which possessed teats, but 
hardly any areolae. Above the supernimierary teat of the left 
side there was another one showing distinct orifices. Glandular 
tissue could be discerned below all five teats, and many accessory 
apertures were found in the areolae of the normal breasts. In 
the twenty-one years of her married life this woman had given 
birth to twelve children, twins being born twice, and had had 
seven advanced miscarriages; she had thus passed through 
seventeen pregnancies. All the breasts yielded milk, but a 
child could only be fed from the normal ones, since these alone 
were furnished with teats which could be seized by it. 

Hansemann records in his treatise 262 cases in all : 81 males, 
104 females, and 77 in whom the sex is not stated. The author 
refers to the goddesses Isis and Diana, who were represented 
with many breasts as a symbol of fruitfulness ; but he rightly 
adds that, judging from data of the present day, the myth can 
have had no foundation in fact. 

I have to thank my pupil Kenkitzi Horiuchi for the record 
of a case of polymasty, published in the Weekly Medical Journal 
of Tokio, of 4th July 1891 (No. 692), which may be added to 
Hansemann's series. It is that of a Japanese girl, aged nineteen, 
who was examined in the hospital of Fukui. Above the normal 
well-developed teats, at a distance of 4 cm., there was on each 
side (Fig. 14 m") an accessory teat of the size of a pea, dark in 
colour, and in all respects like a true nipple. Above, and at 
some distance laterally from the normal breast on each rfide, 
a second smaller breast {m") was found, with a teat. Fig. 14 is 
taken from a photograph of this case. The girl was in all other 
respects normal, and menstruation began at the age of fifteen. 

In conclusion, I append some observations for which I am 
indebted to Otto Ammon, of Karlsruhe, distinguished for his re- 
searches into the anthropology of Baden. The data were obtained 
in connection with the recruiting for military service in the 
year 1890 ; and the manuscript bears the title, "Some Observa- 
tions on the Occurrence of Supernumerary Teats, and on the 
Direction of the Hair on the Breasts." Out of 2189 men (of 



TEGUMENTAL ORGANS 



21 



the Donaueschingen military district) supernumerary teats were 
found in sixty-six cases, one extra teat in sixty-two, and two in 
four, giving a proportion of one case in every thirty -three. 
Besides these sixty-six cases, forty-eight others showed traces of 
supernimierary teats, in the form of circumscribed patches of 
pigment (small areolse). The nature of these patches was indi- 
cated by the fact that while on one side of the body there was 
the pigment patch and the teat, on the other, symmetrically 




Fig. 14. — Case of Polymasty in a young Japanese Girl nineteen years old. 

m', normal teats ; m", supernumerary teats on the normal breasts ; m'" , supernumerary 

teats on accessory breasts. 



placed, there was merely the patch. This condition was so often 
repeated, that there could be no doubt that these patches, situated 
as they were along converging lines, were the homologues of 
teats in an advanced stage of degeneration. 

The above-named sixty-six cases, together with the forty- 
eight others in which only traces were found, testify to the 
occurrence of rudimentary mammary organs in various degrees 
of development in 114 of the 2189 men examined, i,e, in the 



22 THE STRUCTURE OF MAN 

proportion of 1 in 19. In every nineteenth man, then, we find 
the atavistic reappearance of supernumerary mammae. 
The following is an analysis of these cases : — 

On the right. On the left. 

One teat .... 24 cases. 36 cases. 

Two teats .... 3 „ 3 „ 

Other combinations ... 2 >) ^ » 



One trace .... 8 » 35 „ 

Two traces .... 3 „ 7 „ 

Other combinations ... 2 „ 2 „ 

The preponderance of teats on the left side is as 1*4 to 1, 
and in the case of traces of these organs it is still more striking, 
viz. as 3'38 to 1. This is no doubt to be associated with 
the well-known fact that the normal left breast in women is 
often (always?) more developed than the right (cf. ante, p. 19), 
and it may be that the right, therefore, degenerates more rapidly 
than the left. 

In those cases recorded in the literature of the subject in 
which one of the normal teats is entirely absent (amasty), the 
right nipple is more frequently wanting than the left. 

In the cases recorded by Ammon (if we reckon together the 
nimiber of teats and teat traces occurring singly) the proportion 
of those on the left to those on the right is 71 to 32. These 
results agree pretty closely with those of Leichtenstern. 

In one of the cases with a pair of supernimierary teats, 
Ammon found these considerably to the side, quite near the 
anterior axillary fold formed by the edge of the pectoral muscle ; 
and in a case described by Leichtenstern they had even entered 
the axillary area. 

This shifting apart is explained by Ammon as connected 
with the upright gait of Man, i.e. with the position of the upper 
extremities, which is secondarily acquired as a result of it. 

The following case, observed by Ammon, is particularly 
interesting, as a striking example of the extraordinary persistence 
of certain organs which, after becoming as a rule extinct, 
occasionally reappear. 

On the upper part of the breast of a very hairy soldier, two 
diverging hair vortices occurred a few centimetres above the teats, 
but farther apart than these, and nearer the axillary folds (* Fig. 
15). At the focal point of each of these vortices there was a 
light spot from which the hair grew upwards and outwards as 



TEGUMENTAL ORGANS 



from the crown of the head. These were evidently the sites of 
former teats — that is, of former orifices ; for, as .{Unmon rightly 
remarks, the hair vortices agree with the diverging vortex 
fomid at the point where the canalis sacralis finally becomes 
closed — the glabella coccygea, or " sacral dimple," which lies above 
1 vortex. This latter, however, is a converging vortex. 




Fio. 15. — FaoKT VIEW of the Body of a Hospital A 

HALF YEAFS OLD. (After O. Amtnon.) 

m', nornial teats ; *, bair voctices above these, pointing to the farmer presence of 

superaumerar; teats. 

such as always occurs where a protuberance formerly existed (cf 
ante, p. 5) ; but the glandular area of the breast, as Ammon further 
rightly argues, originally developed not as an elevation, but as a 
depression, out of which the teat rose up secondarily. According 
to Ammon there are, on the normal teats also, smaller diverging 
vortices, in which "the hairs course round and round the areolie . . . 
but these are soon lost in the general course of the hair tracts." ^ 

' I here reprint b; perxnisaion a. letter received from Herr Otto Ammon, on the 
10th February 1892. I have refrained from commenting upon it, as I have not jet 
been able to confirm the obsemtian recorded : — 

'i Allow me to draw jour attention to another case which I have not yet recorded. 



THE STRUCTURE OF MAN 



The most interesting case yet recorded by any author, a 
case which is in fact unique, is that of a Tribei^ reoroit 



FiQ. 16. — SCHBBIHBBVOM ScHOHACH, aged twenty-two and a half, serviDg in I6th Baden 

Infantry Regiment, K. F. III. No. IH. (After Amnion.) 

m', normal teaXa ; ta", siipemnmerar; teata ; via', superaumeraiy teat areas above 

the normal breasts ; ina', the same below the nonnal breaatB. 

examined by Ammon. In this man (Fig. 16) there were four 
pairs of teats and teat traces. Above the normal teats (m) 
there were two teat areas (bilaterally symmetrical pigment spots, 

As I am not sure of its significance, I simply giva the facts, leaving you to decide 
whether it is anything move than a chance occurrence. In very hairy men there 
are often found all over tlie ventral surface small hairs (0'5-I*0 cm. long), disposed 
in the middle line lengthwise and at the sidca horizontally, which gradtlally bend 
round and converge towards the navel. Above the navel they point downwards, 
below it upwards. The ordinary course of these hairs is broken at points where 
longer and stronger hairs grow, and these points occur where in other individuals 



TEGUMENTAL ORGANS 26 

ma') lying in shallow depressions of the axillary folds, and thus 
still more lateral in position than in the case above described 
(Fig. 15). In descending order, below the normal teats, came a 
pair of tolerably distinct though small teats with areolae (m") ; 
and lowest of all two small rudiments (bilaterally symmetrical 
pigment spots, ma") lying below the ribs. 

This case suggests that the demonstration in the himian 
embryo of a mammary line or ridge like that above described in 
the quadruped may be only a matter of time.^ 

supernumerary teats appear ; they lie, however, below the normal teats, while in 
the man in your large photograph (Fig. 15) they lie cbbove these. 

"The greater development of hair at those parts of the body which correspond 
with the position of supernumerary teats below the normal ones, i.e. on the con- 
verging lines, has twice been observed by me, and in each case on both sides of 
the body. The stronger hairs do not form tufts, but lie parallel and close 
together, and follow the general course of hair, i,e. have the same direction as the 
rest ; they are merely longer ^ thicker^ and perhaps also darker. The fact that they 
do not form vortices deterred me from connecting them with rudimentary teats. 
The facts, however, are worth recording." 

^ Further information on the subject of supernumerary teats and mammary 
gland, can be obtained from the works of Mitchell Bruce {Jour. Anat. and Phys., 
vol. xiii. p. 425) and Karl von Bardeleben {Verhandl. d. Anatom. Gesellsch.y Miinchen, 
1891 ; and Wien, 1892). I would, however, warn inquirers against the danger of 
seeing a teat in every wart-like prominence ! 



THE SKELETON 

The Vertebral Column 

The vertebral column of an adult human being consists normally 
of thirty-three to thirty-four vertebrae, nimierical variation being 
due to the inconstancy of those of the coccygeal or caudal series. 
As might be expected from the study of other related organs {e,g. 
the vertex coccygeus, the filium terminale, the arteria sacralis 
media, certain muscles and nerves, and the coccygeal gland), 
we here meet with evidence of degeneration and variation. This 
is specially the case during development. It is, above all, the 
caudal region which, in this respect, has claimed the greatest 
attention of morphologists ; and incidentally to the study of this 
there arises the old controversy as to whether Man or his 
ancestors possessed a tail. 

At an early stage of development the human embryo 
possesses at the posterior end of the body, clearly in direct 
continuity with its developing axial skeleton, a free projecting 
pointed appendage, bearing an undeniable resemblance to the tail 
of a lower animal. This is delineated in Fig. 17, cd., and will 
be further discussed as we proceed. At later stages of develop- 
ment this organ is less conspicuous ; it gradually becomes shorter 
and blunter, and is slowly, as it were, taken into the trunk. 
For some time, however, a caudal prominence remains; but 
this at last either disappears altogether, or leaves, at the point 
where its tip abutted against the integument, more or less 
distinct traces known as the " vertex coccygeus " (cf. arUe, 
pp. 5 and 7). This is the normal course of development, but 
occasionally a tail-like appendage is found in extra-uterine life. 
An extensive literature exists on this subject,^ and to it I 

^ Some of the alleged obserrations on this subject are not such as to awaken 
confidence, and others refer to pathological cases or abortions, in which, among 
other malformations, more or less developed caudal appendages occurred. Other 



TEGUMENTAL ORGANS 27 

must refer the reader, as I can here only call attention to a few 




Fiu. 17.— Two YouNQ Human Eubrtos 
A, ventj-Bl ; B, lateral view, (After Echer ) Both flgiires are intended to show the 
freely projecting taQ (cd.). cp-^ head la eye ap fore limb ap hind-limb; 
C.U., umbilical cord. 

Gerlach records a very remarkable ease of tail formation 
in an otherwise normal human embryo, in the fourth month 
of intra-uterine life, an age at which, as a rule, the tail-like 
appendage has disappeared. The length of the trunk was 7"6 
cm., the total length 10'8 cm. ; and as the tail (Fig. 18), which 
projected freely from the buttocks, measured from root to tip 17 
mm., it was almost a sixth of the total length of the whole 
embryo. At its thickest part, where it left the body, it was 2 
mm. broad, and it thence gradually narrowed towards its middle. 
Closer examination revealed the following facts: — The caudal 
appendi^ was not only connected with the last (fourth, and still 
cartilaginous) coccygeal vertebra, but the chorda dorsalis could 
be distinctly traced within it. Muscle bundles were also found, 
which from their whole position could be compared with nothing 
else than the M. curvator caudse of the lower animals, i.e. with 
a true tail muscle. The existence of muscles further justifies 

mare recent observationa, again, have been made on living subjects, where 
nfttiiraUy no precise anatomical data could be obtained. One point can be main- 
tained with certainty, viz. that in some of the observed cases, e.g. in those of de 
Usillet, a hereditary tendency was evident 



28 



THE STRUCTURE OF MAN 




Fig. 18. — Tailed Human Embryo. 
(After Gerlach. ) 



the assumption of the former presence of " proto- vertebrae " 
[or mesoblastic somites] in this region, and these, in turn, might 

indicate the prolongation of the spinal 
cord into the caudal region in earlier 
embryonic stages (c£ Fig. 20). 

We must not, however, assume, as 
Gerlach justly observes, that a true 
tail, supported by skeletal tissues, 
would have developed in this embryo 
had it lived longer; because the 
tissues lying in the region of the 
caudal filament showed no traces of 
conversion into permanent cartila- 
ginous or osseous vertebrae. It was 
further observed, that at the point of 
junction between the posterior coccy- 
geal vertebra and the proximal end 
of the caudal filament, the chorda dor- 
salis had already disappeared. These 
facts indicate an attempt to retiu'n 
to the normaA The tail showed every 
sign of degeneration ; but this does^'not detract from the great 
morphological interest of the case, which has led me to describe 
it at some length. 

Three other certified cases of tail formation in human beings 
may be cited. 

The first is that of an Esthonian recruit, described by Max 
Braun in vol. iv. of the Zoologischer Anzeiger, The coccyx, in 
this case, did not recede into the groove of the buttocks under 
cover of the nates, but ended in an eminence, which, though not 
long, could be laid hold of and felt by the fingers. Thus exa- 
mined, it was found to lie in a direct line with the vertebral 
column and to contain distinct vertebrae, the last of which was 
about the size of a pea. It could not be certainly ascertained 
in the living subject whether this tail was due to numerical 
increase in the number of vertebrae, or simply to a retention of 
the embryonic straight condition of the coccyx itself. It is a 
noteworthy fact, however, that Ecker's glabella and foveola 
coccygea, or sacral dimple, had persisted. 

The second case is that of a newly-born female child, recorded 
by Lissner in 1872. Here also hard, irregular bodies, somewhat 
like the phalanges of a finger, could be distinctly felt in direct 



THE SKKLETOS 



^*^N 



axial continuatioQ of tbe T^nebial colomiL TwelTe years later, 
when tbe caadal appendage had reached the length of 12'5 cm., 
these coold still be detected' 

I have to thank my friend and coUeagne, ProfesBor G. R 
Howes, for the knowledge of the 
third case.* It is desfrribed in tbe 
Scieidifie American of Mav 11th, 
1889, p. 296, where an engraving 
taken from a photograph is also 
given. Fig. 19 is a copy of this, 
and represents a jonng Moi, twelve 
years old, who possessed a tail- 
like appendage 1 foot in length, 
and soft and smooth to the touch. 
As no skeletal elements could be 
felt, a prolongation of the vertebral 
column was certainly not present 
It cannot therefore be considered 
a true tail, and this conclusion ap- 
plies to a large number of Bimilar 
formatioDS which have erroneously 
been regarded as tails [some of 
which are purely pathological and 
due to spina bifida]. 

With r^ard to tbe number 
of caudal vertebrte definitively 
formed in Man, Steinbach has ar- 
rived at the following conclusions, 
after working upon a great ac- 
cumulation of material 

The male embryo, from the end of the second month of intra- 
uterine life, has five post-sacral vertebrse; and indications of com- 

' It is importent also to note that similar reversiousr; fonuatious liavn oii>iuiiUi- 
ally been observed in the Anthropoid Apes (Gorilla and the Oraiig), anil this is th« 
more lematlcable, as in the latter the degeueratiou of the oa roory);'''' wliioh niliailta 
as ft rule of only three vertebrse, haa gone still further than in Man. [It \» worlliy 
of remsik beni that this same maximum reduction of the uaiiilal vi'rttiblw In tbrm 
oGcnn alio in some Bats, and that the opposite extreme for thi> uiaiinnallaii uri'lm U 
naohed bj a smalt insectivore from Madagascar (MixrogaJt hiiginiuJnltA and ihd 
long-tailed Pangolin {Mania matruTa) of the old world, iii vrliirh tliM miuUI vi'Vtvluw 
may be close upon fifty in number.] 

' [And I, in turn, have to thank my friend Profewior •loliiiiuiii SvnilllHti'll, itf 
Qneen'a College, Belrast, in conversation with whom my attontliiii wan llrar iIihuii 
totUaeMB.— G. B. H.] 




"TiiLKD" Child, Moi, 



THE STRUCTURE OF MAN 



meocmg fusion between the last two of these sometimeB occur. 
Six vertebr* were once observed in a boy four weeks old ; and 




PlO. 20a. — DlAOHiMMATIC RECONBTHUCTIOM OF THE TAIL EHD OP A 

Human Eubrto (length of trunk, 8 mm.) 
ch., DDtDchord ; n., Wolffian tubule ; u., duct of primitLve kidney ; a^, inteattne ; ilf, 

^ urinary bladder ] m.a., anal membra.Be ; md, medullary tube ] alf, poat-anal gnt ; 

JT, neck of allantois ; (:.«,, umbilical cord. (After Keibel.) 



jr W" 




Pre. 20b. — DiAOBAUHATio Rkcosbthuction of the Tail End of a Human Embkto 
YOUNOKB THAN FlQ. 20a (entire length, 4 mm.). {After KeibeL) 

Lettering as above ; in addition c.c, caudal limit of the etelom ; a.c, caudal limit of the 
bind'limb ; i-ii, tine drawn through the anterior limit of the taiL 

Leboucq bas recorded the same number in an embryo 25 
mm. long. The opposite extreme is reached where only three 



THE SKELETON 31 

vertebrae occur. In the adult man the regular number of caudal 
vertebrae is five, whereas the number may be either four or five 
in the adult woman.^ 

In the female embryo four such vertebrae are found as early 
as the end of the third month, and the end of the caudal portion 
of the vertebral column is in the female at all times more liable 
to variation than in the male. On the other hand, the whole 
vertebral column of the female is much more constant, with 
regard to the limits and detailed characters of its separate 
sections, than that of the male. 

The complete development of the caudal vertebrae is not 
concluded at birth, for their ossification has not then commenced ; 
they are in this condition subject to the most varied influences, 
which may cause further fusion, reduction, or deviation from the 
sagittal plane (lateral curvature of the terminal vertebrae) (cf. 
Fig. 24). 

But what defines the human tail ? In answering this ques- 
tion we cannot do better than follow Keibel, who rightly points 
out that the definition of the tail in human anatomy must be 
in strict harmony with that of Comparative Anatomy, and that 
therefore so much of the vertebral column as is posterior to that 
(sacrum) which attaches the pelvic girdle is caudal. Since, 
however, the relation of the limbs to the axial skeleton is of a 
secondary nature. Comparative Anatomy cannot help us in the 
important early stages. We can only deal with this difi&culty 
by dividing up the body of the embryo into regions, each con- 
taining a certain number of segments, and in so doing we cannot 
avoid ascribing to the regions the number of segments which 
are found in the adult. In Man, therefore, whom we are now 
considering, we refer the first seven vertebrae to the cervical 
region, and the twelve which foUow to the thoracic ; the lumbar 
and " sacral " regions each have five, and the remainder belong to 
the caudaL 

In all Vertebrates, however, a shifting of the pelvic girdle 
which occurs during embryonic development has to be taken 
into account ; and in this case the definitions borrowed from 
the adult are not altogether applicable. His, Fol, and Keibel, 

^ The most reduced vertebral columns are always those of females. Sexual 
requirements probably account for this, and for the fact that sjmostotic union of the 
first coccygeal with the last sacral vertebra is less frequent in females than in males. 
In the latter, the connection between the comua sacralia and coccygea may even 
give rise to a fifth pair of sacral foramina, and in such cases the sacrum appears to 
consist of six vertebrae. 



32 THE STRUCTURE OF MAN 

agree in attributing to human embryos of 4 to 6 mm. an externally 
visible and segmented tail, with a nervous axis and a post-anal 
gut (cf. Fig. 20b), in comparison with which the peculiar perma- 
nent internal tail of the adult is a very degenerate organ. In 
this early embryonic stage the tail consists of only two or three 
segments, but at a later period there are six caudal segments, the 
terminal mesodermal mass being reckoned merely as one. At 
this stage the tail consists of a number of segments, which are 
but very rarely retained permanently or even for a long time. 

The post-anal gut seems to be constricted off from the cloaca 
at this stage, but it is continued for the greater part of its course 
along the whole length of the embryonic tail. • It apparently 
reaches its maximum length at this period (cf. Fig. 20, aZ"). 

At a later stage of development also, when thirty-six 
somites or body segments are formed, the post-anal gut can still 
be traced, but is no longer tubular. The caudal region at this 
stage possesses four spinal ganglia with three related nerves. At 
a later stage the post-anal gut degenerates altogether. 

To sum up, we have the following purely anatomical facts 
which indicate that Man's ancestors possessed a tail : — 

(1) The coccyx of the adult consisting of three to six caudal 
vertebrae. 

(2) The two caudal spinal nerves. 

(3) The caudal musculature, the existence of which, further, 

is a direct proof that the tail was external and func- 
tional (cf. p. 27). 

(4) The vortex coccygeus and the foveola and glabe6S£i 

coccygea (cf p. 5). 

(5) The variability of the caudal region in general. 

The other divisions of the human vertebral column also 
furnish many interesting points. One of the most characteristic 
peculiarities of the human backbone is its typical mode of curva- 
ture. The lumbar portion (cf Fig. 23, B), which extends to the 
promontory of the sacrum and is convex anteriorly, deserves 
special attention. This lumbar curvature might appear to owe 
its origin to statical and mechanical causes connected with the 
upright gait, but while it is less markedly developed in the 
anthropoid Apes, [it has been shown by Cunningham and Charpy 
to be at least anticipated in certain quadrupedal Mammals].^ 

^ [Huxley was the first to appreciate the existence of the lumbar curvature in the 
anthropoid apes, and Cunningham, Turner, and Symington have more recently drawn 



I THE SKELETON 33 

Of special interest, however, are the variations of the separate 
visions of the vertebral column, in relation to other parts of 
e skeleton which have become secondarily attached to it, sueh 
the ribs and the pelvic girdle. These variations, though 
ected ontogenetically, have a phylogenetic significance, and 
ay therefore he described in further detaiL 
■ Although the pre-sacral portion of the column consists normally 
of tweuLy-lbiir vertebrse. Embryology and Comparative Anatomy 
show thiit tbid cannot be regarded as a primitive condition, and 
that tht.' jielviB formerly lay much farther back than at present, 
that is, tliat the trunk was originally longer than now. (We 
lUbWl see liiter that a more extensive body-cavity or cojlom was 
Bfiected with this greater length of the vertebral colnmn.) 
'jKoseuberg has demonstrated that in the course of human 
TllopmenC the first sacral vertebra becomes incorporated in 
L later than the second, and that later than the third. 
And further, since a primary relationship between 
i yertebrie which become the two anterior coccygeal of the 
, fl^tt :ind the developing sacrum is discoverable, it is evident 
'*"'*% while new sacral articulations are formed anteriorly, detach- 
niflitt of vertebrffi which were formerly sacral takes place 
Jeriorly, the latter being transformed into coccygeal vertebtse.' 
mrward shifting of the sacrum and pelvic girdle is thus onto- 
mtically proved. 

le detailed differences iu the condition of the lumbar vertebrae of tbe 
niveau and certain dark-skinned races, and the anthropoid Apes.] 

" am Laa shown (Mem. H. Irish Acad.^No. II. 1886) that Acby's denial 

ie of a Inmbar curvature in the Gorilla ia untanabla. His own test for 

Iwibar ourvatnre is a line drawn from the centre of the anterior border of the 

ner surface of tbe tirst lumbar vertebra to the centre of the anterior border of the 

r surface of the last lumbar vertebra. The distance of the moat prominent 

1 the veutral surface of the lumbar section of the column from this line, 

ftltiiJied by ona hundred and divided by the length of the line, givaa the index 

I cui-vature, ] Little ia known concerning the lumbar curvature of the savage 

IS of mankind i but the cousins Sarasin, on the examination of dried skeletons 

I the Veddahs of Ceylon, report the lumbar vertebra to ho distinctly concave 

Ltenorly. [Prom what has been said above, it would appear more than prabable 

it the application of the Cunningham method to the atudy of the Veddah back- 

n the ftesh or specially prepared state, would reveal a lumbar curvature aoconl- 

:o the nbove, its most recent and rigid, deBuition. And, from what ie known of 

■ backbonea of other races (ex. the Australian), it would appear probable that 

^tnervation of the Saraains is rather indicative of a greater suppleness of tlie 

n during iifc, induced by habitual resort to certain postures, such as squatting. 

M a greater compression of the vertebrs, and a corresponding greater 

vards obliteration of the curvature after death.] 

t indications of a shifting of the pelvic girdle are traceable in the lower 
ft also, ench shifting being in some cases in a proximal and iu others in a distal 



34 THE STRUCTURE OF MAN ^ 

These changes come to an end when the tweaty-fifth 
vertebra, by virtue of its apposition with the hip-girdle, becomes 
the first sacral, and the promontory attains its full differentiation 
between it and the last lumbar vertebra, i.e. between the twenty- 
fourth and twenty-fifth vertebrse of the whole column. This 
later assimilation anteriorly of sacral vertebrse is further evident 
in the fact that synostosis between the separate parts of the 
sacrum always takes place from behind forwards. 

The tendency of the human pelvic girdle to extend even 
farther forwards is revealed, in eases in which the last or fifth 
lumbar vertebra enters into the constitution of the sacrum. The 
number of pre-saeral vertebra is in such a backbone reduced to 
tweuty-three, and this is the normal condition in the Orang and 
Chimpanzee, and the general, though not the invariable, condition 
in the Gorilla.^ This change is accompanied in Man by the 
depression of the promontory, which becomes duplicated (Fig. 21, 
C C"). The sacrum appears deeply sunk into the pelvis ; 
although such sinking may also occur, as is shown in Fig. 21, 
A' A" without any incorporation of the fifth lumbar vertebra in 
the sacrum. In both cases the iliac crests rise almost to a level 
with the upper edge of the penultimate lumbar vertebra (i.tii. 
of Figs.). 

In contrast to this reduction of the lumbar vertebrae to four, , 
the shifting of the pelvic girdle during development may be 
arrested one vertebra behind the nonnal ; in such cases. whi| 
are rare, we have twenty-five pre-sacral vertebrae. This 
become the nonnal condition in the Gibbon {Hylohates). 

Similar variations are found in individual Oranga, Goril 
and Chimpanzees. In the Orang and Gorilla, for instance, til 

direction. Credoer, by comparing yoang with old BpecJmens, has proved I 
iu a fossil Amphibian (Braiuhiosauriis) a distal shifting of the pelvic arch along si 
to seven vertebne took place ontogeiietically. 

' [111 this animal, the last lumbac veitebra, although it may take on the relatioj 
ships and detailed structure of a sacral vertebra, always retains its independeii 
(i.e. it does not become co-osaified with the other vertebra of the sacral series as in 
the Orang and Chimpanzee). The presence of a highly differentiated articulation 
between the last lumbar vertebra and the anterior border of the Uium is an inTariable 
characteristic of certain Armadillos. Thejointthus formed is a transverse one, which 
comes into especial use when the animal rolls itself up, and is therefore of a purely 
adaptive nature. It is well to guard against confusion between this couditiou and 
that of incorporation of lumbar with sacral vertebrs under extension or forward 
ti'anslocation of the hip-girdle, in which the extra articulation is a longitudinal 
one lying on the inner border of the iliac head. (Cf. Symington, Jimr. A-aat. 
and Fhys. vol. xsiv. p. 42. ; and Paterson. Trans. £. Dublin Soc., vol. v., S«r. 2, 
p. 123.] 




Fig. 21. —The Pelvis. 
A' A", with depressed ; B, with higli standing praniantary (A' ventral view ; A" and B, 
mediRn latitudinal sections). In A" the highest point of the iliac crest almost reaches 
the level of the upper edge of the penultimate lumbar vertehra {l.tv.). In B, on the 
contrary (which is the origiDal condition, and tliat still found in children], the upper 
adgg of the last lumbar vertelira {/.r.) is hardly reached. C C, pelvis with double 
promontory, caused by agsimiUtion of the last lumbar vertebra with the sacrnm (C'. 
median longitudinal section ; C", ventral view). In the latter the appeai-ances are as 
if tba pelvis had shifted forward along the vertebral column. (After Froriep.) 



36 



THE STRUCTURE OF MAN 



lumbo-sacral boundary may be shifted b«tek a vertebra, and in 
the Chimpanzee even two vertebrae. In the former case the 
position normal to Man is attained. 

It is evident that shifting of the pelvic girdle (and, as will 
be seen later, of the pectoral girdle also) cannot take place 
without concomitant variations in other organs. To this question 
we shall return. 



The Eibs and Sternum 

Two types of variation of the thorax are to be distinguished 
in Mammals, a primary and a secondary type. The former is 




A B 

Fig. 22. — A, Transverse Section op the Thoeiax op a Lower Mammal (or of 
' THE Human Embyro) ; B, the Same of a Man. 

In the former it is the vertical diameter which is the greater, in the latter 
it is the transverse, as indicated by arrows. 

far more common than the latter, and is foimd in most Mammals, 
including the lower Apes. The thorax of this primary type (Fig. 
22, A) is elongated, its dorso-ventral greatly exceeding its trans- 
verse diameter (carinate or keeled type). 

The secondary type (Fig. 22, B) is found in Anthropoid 
Apes and in Man. The dorso-ventral diameter is here greatly 
diminished and the transverse is increased in proportion; the 
broad thorax is somewhat barrel-shaped, and often compressed 
antero-posteriorly. This secondary type is preceded, both onto- 
genetically and phylogenetically, by the primary. 

It is evident that the associated modifications, viz. the 



THE SKELETON 



37 



shortening of the thoracic wall, the shifting of the thoraco- 
abdominal boundary, the changes in the axial skeleton, and the 
numerical reduction of the thoracic metameres, must have a far- 
reaching influence on the whole anatomy of the trunk, e.g. on the 
position of the thoracic viscera (lungs, heart), and on the relation- 
ships of the pleural cavities. Thus Euge has shown, in a series 
of excellent papers, that as the secondary type of thorax begins 
to develop, the pleural boundary gradually recedes along the 
anterior and inner wall of the thorax, so that the heart, which in 
the primitive thorax almost always lies remote from the sternum, 
approaches nearer the anterior thoracic walL As a consequence 
of this, the anterior edges of the pleural sacs, which are primarily 
apposed behind the sternum, are forced apart, so that in Man, for 
example, they are often separate as high as the fourth rib. 



cf,^. 




t 



A B 

Fig. 23, A and B. — Diagrams of the Vertebral and Costal Skeleton. 

A, IH THE Quadruped ; B, in Man ; the arrows indicate the line of direct pressure 

of the thoracic viscera upon the wall of the thorax. 

Among the various factors recognisable as having played a 
continuous rdle in the evolution of the Primates, not the 
least weighty is the assumption of the upright position. The 
alteration in the shape of the thorax alx>ve described, by shifting 
back the centre of gravity of the body, favours the upright 
position; and the inter -dependence of these two niodificationH 
is evident 

To the same category, it appears to me, Ijelongs thci gradual 
diminution in number and size of the sternal ribs. It is easy 
to see how, with the shifting of the centre of gravity towards 
the dorsal side of the body, and a consequent diminution of 



38 THE STRUCTURE OF MAN 

pressure on the ventral, the ribs which in the quadrupeds are 
the more necessary for enclosing and supporting the viscera, 
might degenerate in the abdominal or lumbar region. The 
pressure of the viscera is no longer in the ventral, but in the 
caudal direction (cf. Fig. 23). We find, in consequence, a 
compensating expansion of the iliac fossae of the bones of the 
pelvic girdle. The fact that this change is specially pronounced 
in women is easily explained by fimctional (sexual) adaptation, 
and it thfis tends to confirm the above theory. 

The shifting of the centre of gravity towards the dorsal 
side explains why the vertebral ends of the lowest ribs are so 
firmly attached, and also why the dorsal portion of the thoracic 
bony skeleton is much longer than the ventral In this con- 
nection we have naturally to take into account the great muscles 
which are statically and mechanically required by the axial 
skeleton, and for which these ribs furnish points of origin and 
insertion. But even supposing that the ribs were not required 
for this purpose, there are other related structures which, to a 
certain extent, favour their persistence. The chief of these is 
the serratus posticus inferior muscle, which is inserted into the 
four lower ribs, and the latissimus dorsi which partly arises from 
the last three. 

It may be remarked, however, that the mere presence of 
these two muscles, as will be seen later on, is insufi&cient to 
account for the persistence of the lower ribs. Indeed, the latter 
might well be degenerating so far as the former are concerned, 
for not only is the serratus posticus inferior distinctly rudi- 
mentary, but the parts of the latissimus dorsi attached to 
these ribs are quite insignificant in comparison with the rest 
of the muscle. But, notwithstanding this, the action of the 
serratus to a certain degree favours the retention of these ribs 
(cf. p. 45). 

Eeturning now to the more important factors which deter- 
mine the transformation of the thorax, we must, as Euge rightly 
points out, take into account the influence of the fore-limbs. As 
the latter developed into seizing organs, their muscles became 
more powerful and more specialised, and reacted, in turn, on the 
form of the ribs and the arch of the thorax. Further conse- 
quences of this are seen in the greater compactness of the internal 
organs, in the gradual fusion of certain lobes of the liver and 
lungs, and in the approximation and final union of the peri- 
cardium and diaphragm, which may also imply the gradual 



THE SKELETON 39 

depression of the heart. It is, moreover, evident that the 
change undergone by the heart and diaphragm, due to the 
forcing of the former out of the median plane and the shifting 
of its longitudinal axis towards the ventral and left side of the 
body, must again react upon the form and limitations of the 
pleural cavities. 

Slight changes in the limitation of the pleural cavities occur 
also in the lower Mammals; but how far these may be related 
to each other, or in any way to those occurring in the Primates, 
is not very clear. The original causes of the changes are 
very various, but their close dependence upon the skeleton is 
evident. 

The tendency towards a gradual diminution in the number 
of ribs, previously referred to, requires further consideration. 

The presence of free ribs, as is well known, distinguishes the 
thoracic vertebrae of the adult from those of the cervical and 
lumbar regions. The limits of the thoracic region, however, are 
liable to variation, akin to that already described as occurring in the 
lumbar and sacral regions. Twelve pairs of free ribs are present 
normally in Man, as in the Orang, but a comparison with other 
(and chiefly lower) Vertebrates points to the earlier existence of 
a larger number. This view is supported by Ontogeny, as well 
as by the occasional occurrence of so-called supernumerary ribs. 
These are less frequently found at the upper than at the lower 
end of the thorax; and in either case, the thirteenth rib is 
subject to great variation both in form and size. For example, 
a thirteenth rib at the lower end of the human thorax may vary 
in length from 2 to 14 cm. ; but thirteen is the normal number 
of ribs in the Gorilla and the Chimpanzee, and Hylobates has 
thirteen or fourteen. Where a free rib is borne by the seventh 
cervical vertebra, the number of these vertebrae naturally appears 
to be reduced to six. Where a thirteenth rib occurs in the 
thorax, the lumbar vertebrae similarly appear to be reduced to 
four — ^unless the embryonic forward shifting of the pelvis has 
been arrested at the twenty-sixth pre-sacral vertebra, as is not 
unfrequent under these circumstances, for it has been observed 
that the thirteenth rib, which always appears in the embryo, 
begins to degenerate as soon as the twenty-fifth pre-sacral vertebra 
is incorporated in the sacrum. 

We have further evidence that Man has inherited more than 
twelve pairs of free ribs, in the fact that reduced ribs are found 
in the embryo, not only in connection with the first but with all 



THE STRUCTURE OF MAN 



the lumbar vertebrfe (Fig. 24, r.l.), and in the sacral region also 
(Fig. 25, B r.s.y From this it is clear that the pelvis in Man, 




FjO. 24.— PaBT of the TKOBACIC, and the whole LUUBSR, SACBiL, 4KD 

CoccTOEAL Sections of a toung HnMAN Vertebral Column. (Dorsal aapect.) 
The lateral processes of the first to the fifth lumbar vertebrte are on one sidfl prolonged 
(by dotted lines) for di^ranimatic delineation of the formerly existing lumbar ribs 
(r.l.), which are present in the embryo. The sacrum ia still Eubdivided into its liTe 
compOQeut parts, i.e. consists of five distinct vBrl«br» {v.s.). v.c., caudal (coccygeal) 
vertebrje ; T.ih., the three lower thoracic ribs. 



like that of all terrestrial Vertebrates, is carried by ribs, which, 
however, become early united w h the s eral trans erse processes. 



' In the ttrentj-first and twentj-se nd p 
riba are still separated froni the vertebra a '. 
the succeeding vertebn« they are more and m 
would thus appear that the reduced ribs a a y 
verae procesaes of the lumbar vertebrie. 



jj-a bne of the embryo, the 

by memb a us ttsaue, but in 

n p y un ted with them. It 

100 K)rat«d a h so-called trans- 



THE SKELETON 



41 



As already stated, the presence of a free rib in connection 
with the last cervical vertebra (Fig. 27, A) is somewhat rare in 



B 



o-?*. ^r.s. 





V' 



Fio. 25. — Diagram of a Transverse Section of the Hip Girdle and Sacrum : A., of 
A Salamander ; B., of Man (young stage iu which the separate parts of the sacral 
vertebrae are still distinct). 

6. v., body of sacral vertebrae ; a.n., arch of same ; r.s., sacral rib ; i7., ilium ; 

p. J pubis ; C.A., coelom ; ac, acetabulum. 

adults, but the vestige of such a rib, and even of a second (some- 
what less attached) near the sixth cervical vertebra, is almost always 




f.c.t... 




FiQ. 26. — A, First Thoracic Skeletal Segment for comparison with B, Fifth 

Cervical Vertebra (Man). 

c, first sternal rib ; c', cervical (rib which has become united with the transverse process 
{tr.)) the two enclosing the costo-trans verse foramen {f.c.t.) ; zy.^ articular process 
of the arch (zygapophysis) ; 6.v., body of vertebra ; sty sternum. 

found in the embryo. The five anterior cervical vertebrae show 
no such distinct vestiges, although their former presence is clearly 



42 



THE STRUCTURE OF MAN 



indicated by the detailed characters of the transverse processes 
(Fig. 26, b). [In the Platypus {Ornithorhynchtis) reduced 
cervical ribs remain for life distinct on six of the seven neck 
vertebrae, being absent from the atlas only, and one or more 
cervical ribs may occasionally retain their independence among 
the quadrupedal Mammals generally.^] 



.r.cvii. 





.r.th,i 



r.th.iu 



Fig. 27. — A, Portion of the Thoracic Skeleton of an adult Fbmalb 

POSSESSED OF A PAIR OF FREE CERVICAL RiBS. 

The twelve normal pairs of thoracic ribs were present. Length of the right cervical rib 
3-5 cm., of the left 6-7 cm. r.cvii.', vertebral end of the cervical rib ; r.cvii,", 
sternal end of the same, fused with the manubrium stemi (the vertebral and sternal 
ends being in life connected by a ligamentous band, not indicated in the figure), 
r.th., first and second sternal ribs. 

B, Example of the reduction of the first pair of Thoracic 

Ribs (an Adult Male). 

There were twelve pairs of free ribs present, the first pair being reduced both in 
length and calibre. The left of these was 9, the right 8, cm. long. r.th,u', vertebral 
end of the first rib ; r.th.i.", its sternal end, synostotically united with the 
manubrium stemi {st.) ; r.l., fibrous band, formed by retrogression of the missing 
portion of the rib. 

In both figures, I, II denote the first and second thoracic vertebra, VI, VII the two last 
cervical vertebrae. (Adapted from Leboucq.) 

The greatest development of the seventh cervical rib would 
naturally be that of miinterrupted extension round the neck. 
Such an extraordinary condition has only apparently been once 
observed (by P. Albrecht). Cases in which the rib in question 
unites with the first thoracic rib by its cartilaginous extremity, 
before reaching the manubrium, are far more frequent. Some- 
times only the sternal and vertebral ends are found (in either 
a bony or cartilaginous state), the intermediate part being 
represented by a fibrous band. In spite of the reduced con- 

* [Mivart has figured and described (for example) what appear to be practically 
stages in the redevelopment of the last cervical rib on opposite sides of the same 
vertebra of a Binturong {Ardictis), Proc Zool. Soc, Lond., 1882, p. 461.] 



THE SKELETON 43 

dition, however, the internal and external intercostal muscles 
between this cervical and the first thoracic rib are well developed 
in cases like that above figured ; indeed this is so even when 
(as occasionally happens) the fibrous connecting band is wanting 
(Leboucq). The sternal portion of the rib is as a rule very 
weakly developed, sometimes free, sometimes partly fused with 
the first thoracic rib. The vertebral end varies much in form, 
size, and articulation upon the vertebral column ; and further, its 
relations to the firet thoracic rib may, as Leboucq has shown, vary 
greatly. It may either be altogether fused with the latter, merely 
loosely attached to it by connective tissue, or actually articulated 
with it. In the first case, the first thoracic rib appears forked 
at its vertebral end, and this (according to P. J. van Beneden) 
is the rule in many Cetaceans. 

Apart, however, from such cases as these, a further proof of 
the former existence of cervical ribs in Mammals is derived from 
the study of the adult Edentata. Among these, Cholceptis has 
normally only six cervical vertebrae [defined as those destitute of 
free ribs].^ Bradypus inftiscatits and B, tridactylus illustrate 
the other extreme, possessing normally nine such vertebrae ; 
while B. cuculliger has either eight or nine. In the latter 
cases the upper end of the thorax has imdergone greater reduction 
than in any other Mammal. 

The fact that in Man the first thoracic rib is probably 
beginning to degenemte,^ and is at the present time in process 
of atrophy, is established by the not infrequent recurrence of 
imdoubted cases of its abortive development. Such have been 
recorded by Struthers, Grosse, Hunauld, Gruber, Turner, Leboucq, 
and others (cf. Fig. 27, B). The description given above of 
the seventh cervical rib might, in these cases, be applied to the first 
thoracic. Nevertheless, I believe, for reasons to be given later, 
that should reduction at the upper end of the thorax advance, 
it will do so far more slowly than at the lower, or indeed that 
it may even be arrested for an indefinite period (cf p. 45).^ 

* A similar numerical reduction of the cervical vertcbne occurs also in the 
Manatee [but there is reason for believing that it is in that animal due to the 
excalation of at least the body of one of these, and not to the assumption of thoracic 
characters by the last of the series. ] 

* I should like here to raise the question whether this tendency to reduction at 
the upper end of the thorax may not be a determining factor in the degeneration so 
frequently found to be commencing at the top of the lungs ? (cf. infra), 

' It is interesting here to note that ventrally to the transverse process of the sixth 
cervical vertebra, there often arises, on either side, a projection, which might be 
claimed as a vestigial structure, since in most Mammals it stands out prominently 



44 THE STRUCTURE OF MAN 

From the above facts it is sufficiently evident that the 
vertebral column was ancestrally furnished with a far greater 
number of ribs than at present, and that the pleuro-peritoneal 
cavity or coelom was once more capacious both at its cephalic 
and caudal ends. Even at the present time, as already shown, 
its modifications are not permanent. This is manifest, not only 
from the reappearance of (so-called " supernumerary ") ribs, but 
also from the decidedly rudimentary character of the eleventh and 
twelfth ribs, which is rendered evident in several ways, more 
especially in connection with variation in their size. The twelfth 
rib, as might be expected, has a much wider range of variation 
(2 to 27 cm.) than the eleventh (15 to 28 cm.); neither pair of 
these reaches the sternum, and both show degeneration in their 
detailed relationship to the vertebral column. These ribs have 
no tubercle, and, consequently, no costo-transverse articulation ; 
and the articulation of the head (capitulum) of each of them is 
vertebral, instead of inter- vertebral, as in the case of those in 
front of them. Occasionally a tendency to similar conditions 
appears in the ninth and tenth pairs. Ontogeny shows that the 
reduction of the eleventh and twelfth ribs is comparatively 
recent, since the rudiment of the costo-transverse articulation 
(tubercle) of the eleventh rib is still developed in the embryo. 

Turning now to the ensiform (or xiphoid) process of the 
sternum, the variations in its shape, and more especially the 
presence of occasional median fissures or foramina in it, show that 
it arose from paired cartilages. It is, in fact, constricted off from 
the eighth, and possibly also from the ninth pair of ribs. The 
cartilages named, undoubtedly, at one time took part in the forma- 
tion of the " sternal bands " to be described later, and thus the 
number of ribs reaching the sternum may once have been greater 

as a strong process (Gegenbaur). These lower lateral spinous processes [anapophyses] 
which are found only in Hylohates, among Anthropoids, arising from the bases of 
the arches of the last two thoracic and sometimes from the first lumbar vertebrae, 
according to ]3roca, occasionally occur in Negroes. It has been observed, further, 
that the spinous processes of the cervical vertebrae, which are, as a rule, forked in 
Man, are simply pointed in the Hottentots ; and we here encounter a persistence of 
the original simple condition which is normal among Anthropoids (R. Blanchard). 

Finally, it should be mentioned, that the groove on the dorsal side of the arch 
of the human atlas for the reception of the vertebral artery is sometimes overarched 
with bone, and converted into a foramen, such as is always found in most Primates, 
Carnivora, and various other Mammals (Sappey). [And it is here worthy of remark 
that the costo-transverse foramen, and its homologue the vertebarterial canal, may 
in a similar way become completely surrounded by the transverse process 
{Hippopotamus, Man?). Cf. Jour. AtuxL and Phys., vol. xxvii. p. 545.] 



THE SKELETON 45 

than at present. This conclusion is strengthened by the fact 
that the eighth rib not infrequently reaches the sternum even in 
adults.^ 

Eight sternal ribs are found in the lower Apes (which may 
have as many as ten), and may occur in the higher Apes, with 
the exception of the Orang. It is certain that in all Mammals 
those ribs which have their ventral ends in any way attached to 
one another were once connected with the sternum. 

On the other hand, the union of only six ribs with the 
sternum is not rare in Man ; and the existence of this condition 
is a clear indication of the gradual degeneration (shortening) of 
the thoracic skeleton and sternum. In such cases the distal 
end of the xiphisternum may bear two lateral prongs, which 
correspond with the sternal ends of the seventh pair of ribs. 

There are certain considerations which confirm the statement 
above made that the process of degeneration at the upper end of 
the thorax is slower than that at the lower end, to which latter, 
indeed, no limits of variation can be foreseen. We have first 
the rhythmic respiratory mechanism, which is so closely connected 
anatomically and topographically with the complete ribs ; and, 
second, the attachment to this part of the thorax of the 
musculature of the shoulder gii'dle (I refer especially to the 
serratus magnus and the pectoralis major). [These muscles 
under certain conditions play an important part in effecting the 
movements of respiration], and in order to secure a suflScient 
range of activity they must necessarily be inserted into a certain 
nimiber of fixed points. Such points are supplied by the bony 
framework formed by the seven upper pairs of ribs, the sternum, 
and the clavicles; and as long as these muscles remain indis- 
pensable, the bones named cannot well degenerate further. 
We have here a striking example of the important reciprocal 
relation and close interdependence existing between the various 
organs and systems which, so to speak, hold each other in 
check. 

We learn both from Ontogeny and Comparative Anatomy 
that the sternum (which is first formed by the fusion of a couple 
of sternal bands) consisted, in the ancestors of Man, of a row of 

^ [Canningham and Robinson have recorded the existence of an eighth sternal 
rib on one or both sides in 20 per cent of (seventy) subjects examined {NcUure^ vol. 
xxxix. p. 248, and Jaur. Anat. and Phys.^ vol. xxiv. p. 127). In the unilateral 
condition it was found to be dextral in eight out of nine examples ; and Cunningham 
suggests that this may be a reversionary feature, associated with the greater use of 
the right fore-limb.] 



THE STHUCTUBE OF MAN 

:^es. Its early condition is now most nearly retained 
for Mammals among the Edentata [i.e. in the Pangolin (Manisy\, 
and even in the lower Apes extensive remnants of cartilage are 
occasionally present between the bony parts. In most other 
Mammals, the ossific nuclei which appear in the course of develop- 
ment of the sternum are the only indications of its former 
segmentation.^ The fully-developed stemiun of the Primates is 
practically a single broad and firm plate, the solidity of which 
compensates for its decrease in length. 




Fig. 28.— Shodldbr Gibdlk of OBsnHORaTNcapa. 
m.s., mannbrium atenii; c'.,i^,.if,, first, second, tbird ribs ; tt., steniebra ; sc, scapotti : 
m.c, metaoorMoid;' e-c, epicoracoid; d, clavicle ; es'. sudri"., intorclavicle (epjatemnni). 

The origin of the Mammalian interclavicle (so-called epi- 
stemum) is still somewhat undetermined; [but in its position 
beneath (veiitrad of) the sternum proper in the young of the 
Mole {e^.. Fig. 29), in which its development has been most 
fully worked out, and in its relationships to the clavicles, it agrees 
with the interclavicle of Eeptiles.] 

In Monotremes (Fig. 28) the epistemal apparatus (es'. es".) is 
triradiate, and disposed altogether cephalad of the sternum proper. 

' [Approximation of more than one pair of ribs to the post«rior end of the 
sternum ia the rule in many of the lower ^lammaiJa ; in the Rabbit, where two pain 
of ribs always have this relationship, it may or may not happen that a corre- 
sponding extra sternal segment is present in the adult. A careful study of the 
development of that animal's sternum has shown that this segment disappears by 
absorption where not retoined^i.e. that a sternal segment may generally, though 
not invariably, be lost during ontogeny. This fact is of considerable interest in 
relation to the belief in a tendency towards abbreviation of the mammalian thorax 
postero-anteriorly (of. Burne, Froc. Zool. Soc, 1891, p. 159).] 

" [Until recently known as the "coraeoid " ; cf., however, jit/ra, p, 72.] 



THE SKELETON 



47 




In the adults of the higher quadrupedal Mammals, the episternum 
is possibly for the most part represented by a couple of cartilaginous 
tracts, approximated to the sternal ends ^^// 

of the clavicles (es., Fig. 30); and its 
body (es/, Fig. 29), so far as is known, 
appears to become reduced, and either 
closely apposed to or fused with the 
anterior end of the sternum. 

The following information concern- 
ing the human episternum is largely 
drawn from the admirable work of Euge. 

In an early embryonic stage, when 
the cartilaginous " sternal bands " have 
not yet united along their whole length, 
two independent masses, which soon be- Fig. 29.— Episternum of an 

, -1 . , . 1 Embryo Mole. (After A. 

come cartilaginous, appear at the upper Ootte.) 

end of the still forked manubrium sterni. «^-» sternum; es'., central portion 

.^ ,^ , ,, « iP of the episternum ; es.", lateral 

At a later stage they tUSe to iorm a portion of the same ; d., ela- 

single cartilaginous tract, which ejradu- ^icie ; r.c, costal ribs. (The 

_-°., .^iPix ^ii»i iigvLTe was constructed from 

ally interposes itseli between the lorks two consecutive horizontal 
of the manubrium, until finally only sections.) 
the proximal surface of the cartilage projects from that struc- 
ture. As the two sternal ridges fuse completely, the boundary 
lines between the episternal cartilages and the manubrium 
become more and more indistinct, and finally altogether 
disappear, the former structure becoming incorporated in the 
latter. The manubrium of Man is thus a compound of two 
separate structures, one of which is certainly costal and 
derivative of the first pair of ribs. The homology of the other, 
i,e. of the suprasternal portion, cannot yet be decided with any 
certainty. There can be no doubt that we have in it the last 
vestiges of a skeletal structure, but whether they are those of a 
seventh pair of cervical ribs which once reached the manubrium, 
or of the central portion of the episternum of the Monotremes 
and lower Mammalia, must for the present remain undecided. If 
the latter supposition should prove correct, it would point to 
the originally paired nature of the Mammalian episternum, and 
support Gotte's view of its origin from the median ends of 
the clavicles. 

Brechet's cartilages, or bones, which occasionally appear at 
the antero-internal border of the sterno-clavicular articulation, 
and either become closely applied to the sternum or united with 



48 



THE STRUCTURE OF MAX 



it, must not be confonnded with the above-described skeletal 
structures, which are entirelv incorporated into the manubrium. 
These ''ossa suprastemalia " (o^.. Fig. 30) may be derivatives of 
the epistemal apparatus, as Gegenbaur has for years insisted, and 
probably of the central portion of the episternum. The lateral 
portions of this structure are usually homologised with the inter- 
articular cartilages that lie between the sternum and the ventral 
extremities of the clavicles (^.s.. Fig. 30). [There is, however. 




...r. 



.jr.e. 



Fig. 30.— Episterxal Vestiges is Man. 

e.s.y " epistemum " (sterno-clavicular cartilage) ; o.s.^ ossa silprastemalia ; c/., claTicle, 
sawn through ; /'. , inter-clavicular ligament ; T. , costo-clavicular ligament ; m.«. , 
manubrium stemi ; st., sternum ; r.c, first rib. 

still considerable uncertainty about this ; especially as Carwardine 
has recently shown ^ that the ligaments in which the " ossa supra- 
stemalia " lie embedded when free, may or may not be continuous 
with an " inter -clavicular ligament" which, by its T-shaped 
character and detailed relationships, may suggest the inter-clavicle 
(episternum) of Monotremes and Eeptiles.] 



The Skull 

In all Vertebrates the skull may be divided into two 
principal portions, the cranial and the facial The cranial 
portion, or brain case, encloses the anterior part of the central 
nervous system, and is intimately associated with the higher 

^ Jour. Anat. and Phys., vol. xxvii. p. 232. 



THE SKELETOS 



i and tbeir investing capsules. In the embrro it 
is pen^xated for eome distance at its base bv the foreniimer of 
the backbone — the chorda dorsalis. For this reason it appears 
to be in a certain sense a prol<mgation of the axial skeleton of 
the tnink. The A-iscetal or &ciaJ portion of the skull lies postero- 
ventrally to the cranial It is cloaely connected with the pharra- 
geal section of the alimentarr canal, the lateral walls of which 




Fia. 31. — A, SL1GHTI.T DUGKIUHATIC MEDIAN LOSGITUDIML SeC 

Hud asd Astebiob Pobtios of thi TsrsK of a Humax EMBBia sevkstkks 

TO mamriEx teees old. (Afur W. His.; 
^f-, bnia; op., optic vehicle ; md., mAndibtilAr ircb ; jk.- pericardioDi ; od., heail ; {!■., 

moditary Tesicle ; /-/r, bnuicbu) clefts. 
B, Em^TO Tobfcdo, u aeea bv transnulted light. (After H. E. *D(I F. Ziegl«r.) 
of-i olfactory pit ; hy., hyoid arch ; I'., trigeminal Derve : rrf., Vfntricle ; VII, 

VIII, tu-ial and Anditorr nerres ; IX, glosto-phuyngeal nerve. Other refrreuees 

ubrA. 



are, in the embrro, perforated by "gill-clefts" (I-IJ', Fig. 31, 
A), so called because tbeir presence points back to a time in which 
this part of the alimentary caual sened not only for taking in 
food, bat for respiration, as is still the case in the lower Verte- 
brates. That the system of skeletal arches, which alternate with 
these clefts has, in man, undergone considerable modification and 
redaction (c£ Fig. 105) will not appear strange, when the 
biolf^cal conditions are taken into account. The only point of 



60 THE STRUCTURE OF MAN 

essential importance for us here is the fact that the skull of Man 
and all Vertebrates is constructed on a common plan (ef. A and 
E, Fig. 31). 

The fact that this ground plan is not so evident in the skull 
of the higher Vertebrata and Man as m that of the lower Verte- 
brates, is due to the progressive modifacation which the former have 




undergone ; and the final result has been that the human skull 
differs markedly not only from that of the lower Vertebrata, but 
also from that of the Anthropoid Apes, which in the rest of their 
skeleton agree so closely with Man. It will, therefore, be interest- 
ing to examine the two latter types of skull, in order to determine 
and, when possible, explain the differences between them. 

On mere superficial examination, the proportionate difference 
in size between the cranium and the face of the two is most 
striking. In Man (Fig. 32) the cranium is a smooth and imposing 



THE SKELETON 



51 




Fig. 33. — Skull op a Child seven years old. 
(One-third natural size.) 



rounded or oval bony case, which contrasts strongly with the 
incomparably smaller one of the Orang (Fig. 36) and Gorilla, with 
their enormous external 
ridges and protuberances. 
These latter animals, like 
all the Anthropoids, differ 
from Man in the great 
development of the face, 
and especially of the jaws, 
which in Man are sub- 
ordinate to the cranium. 
If, however, young stages 
of the Anthropoid are com- 
pared (Fig. 35), this dis- 
tinction becomes less strik- 
ing; for, as is well known, 
not only the whole head 
but the features of the young Ape bear a decided resemblance to 
those of the human foetus. Indeed, it is certain that the diverg- 
ence begins after birth, the characteristics of each type becoming 
more and more marked as age advances (cf. Figs. 35 and 36). 

The chief cause 
of the distinction 
clearly lies in the 
greater development 
of the human brain. 
In the higher Verte- 
brates the brain must 
be regarded as the 
dominant organ of 
the head; and in 
Man it continues to 
grow even into the 
prime of life, the 
cranial capacity at- 

FiG. 34. — Skull of an Australian from the Murray Gained reaching in 
River. (One-third natural size.) i ^ • 

the male Caucasian 
an average of 1500 cubic cm., and the brain a weight of from 
1375 to 1400 gr. 

With regard to the cranial capacity of the lower races of man- 
kind, observations made by the cousins Sarasin on the Veddahs 
of Ceylon are of special interest. In them, not merely the skull 




S3 



THE STBUCTURE OF MAN 



bnt the whole skeleton is lemarkable for its delicacy, a character 
which, according to Virchow, distinguishes a namber of the wild 
races iDhabiting the islands of the East. The skull is ou the 
average 200 gr. lighter than that of the European: it is very 
small, and the cranial capacity in the pure (unmixed) Yeddah 
male is at most 1250 cubic cm., and in the female some 140 
cubic cm. less than that. 




FiQ. 35.— Skuu. or J 

Orang-Utan. 

(Cnie-thiril Dataral j 

In cranial capacity the Veddahs are undoubtedly among the 
lowest of human beings, and this is quite in keeping with their 
low level of civilisation. The woolly-haired inhabitants of the 
Andaman islands are on approximately the same level, whereas 
the Bushmen and Australians rank somewhat higher.' 

In shape the Veddah's skull is very long and narrow, i.e. 
strongly dolicocephalia The cranium of the female is more 
rounded than that of the male — indeed, all the peculiarities 
which in the European distinguish the skull of the woman from 
that of the man are present in the Veddahs. 

But while there is a difference of from 250 to more than 
500 cubic cm. in the cranial capacity of the Veddah and 
the European, a far greater disparity occurs between the cranial 

' [Id the Akkaa (the pygmy race of Central Africa), the cranial capacity of the 
skull of a mala recently described by Sir W. Flower ia 1102 cubic cm., and that of a 
female 1072 cubic cm. The same writer bae, however, described the skull of a female 
Veddah, having a capacity of but S50 cubic cm., that being one of the smallest normal 
adult human skulls on record (cf. JauT. (^the Anthropalagieal Imlit,, vol. xviiL p. 6).] 



THE SKELETON 53 

capacity of Man and that of the Anthropoid Apes, the latter 
ranging from about 427 cubic cm. (Chimpanzee) to 557 (Gorilla), 
i,e. averaging less than half that of the human races mentioned 
above. As yet no human skull has been discovered which bridges 
over this gap. 

The cause of this great difference lies largely in the fact that 
the brain of the Ape makes no marked progress after birth, and 
this no doubt applies not only to its size, but also to its micro- 
scopic anatomy, e.g. to the differentiation of its gray cortex. 

The Anthropoid skull is furnished with massive jaws con- 
trolled by powerful muscles and armed with formidable teeth. 
This extraordinary development of the facial portion of the skull 
which supports the entrance to the alimentary canal, is no doubt 
of compensatory value in the struggle for existence. We shall 
return to this subject in considering the dentition as a determin- 
ing factor in the modification of the jaws. 

The foregoing account of the changes imdergone by the 
cranial skeleton has, I hope, shown that the human skull is 
subject to the same influences as that of the beasts, and that the 
two differ as divergent adaptive modifications of one and the 
same fundamental plan. This is not, however, an altogether 
satisfactory explanation, since the primary cause of this difference 
of modification (in Man in the psychic and brain-forming direc- 
tion, in the Anthropoids in the vegetative direction) remains 
unknown. 

That these divergent lines of modification from a common 
starting-point were entered upon very long ago is proved, not only 
by the sharply differentiated types of skull found both among 
Anthropoids and Men, but also by the fact that great and un- 
doubtedly atavistic deviations from the general normal type of 
human skull are comparatively rare. The type appears complete, 
well established, and sharply individualised. 

Exception must be made in the case of the dentition, to 
which the above is not applicable, and also in that of micro- 
cephalous and teratological conditions, although these are often 
enough utilised in building up the primitive history of the 
human skull. It is, however, possible, inasmuch as some of these 
cases certainly exhibit phenomena due to arrest of development, 
that an occasional indication of a former primitive condition may 
be revealed in them ; but the pathological element is, as a rule, so 
strong that no certain morphological conclusions can be drawn — 
indeed, deceptive appearances may be expected at every step. 



THE STRUCTURE OF MAN 

Gratiolet has established the fact that the higher races of 




Debb (A), Babooh (B), 



Fib. 3/, — Median Sections through the Head oi 
AND Man (C). 

The relation of the craoiumto the nasal cavity should be noted. The fonner, tdtli gradual 
enlat^ement, cornea to overlie the Utter, thereby altering the facial angle (cf. 
with these Figs. 32-8C). 

men differ from the lower in the order of obliteration of the 



THE SKELETON 55 

cranial sutures. In the lower races, as in the Apes, the process 
always begins anteriorly in the frontal region of the skull, i.e, at 
the fronto-parietal boundaries, and proceeds backwards. This 
naturally causes an earlier limitation in growth of the anterior 
lobes of the brain ; whereas, in the higher (white) races, where 
the fronto-parietal suture disappears only after the obliteration 
of the parieto-occipital one, these lobes are capable of further 
development. This fact may well be closely connected with 
the intellectual difference between the races. It not infre- 
quently happens that the frontal suture remains open ; ^ but 
whether, as might suggest itself, this is to be regarded as 
indicative of a further development or, on the other hand, as 
a reversional feature, cannot yet be decided. On the latter 
assumption, the fact that fusion of the frontal bones occurs in 
many Mammals (Apes, Insectivora, Chiroptera, Monotremata, and 
others) is of interest, especially as reversion to the condition of 
the lower Vertebrates is a phenomenon, which, as we have already 
seen, is by no means unknown in Man. It appears to me that 
the two views may to a certain extent be harmonised, by con- 
sidering that the original independence of the ossific centres 
inherited from lower ancestors may be sometimes retained and 
utilised in the interest of a progressive development of the 
anterior lobes of the brain. 

Gregenbaur, in his Lehrhuch der Anatomie des Menschen, calls 
special attention to the independent ossification of that which 
becomes the postero-inferior angle of the frontal bone, i.e. that 
part of it which borders on the alisphenoid. Since, at birth, and 
even for some time after birth, traces of this division are evident, 
we are reminded of the post-frontal bone of the lower Vertebrates.^ 

On turning to that part of the skull where the parietals 
meet the occipital (the lambdoidal suture), an independent mem- 
brane bone is sometimes found, the so-called "interparietal,"^ 

^ According to Welcker, the frontal suture often persists in Caucasians, less 
often in Malays, and very rarely in Americans, whereas the exact reverse is the case 
with the transverse occipital suture which divides the interparietal from the occipital 
bone proper. It often happens that the latter is found together with the frontal 
suture in one and the same skuU. In the child the fusion of the frontal bones begins 
normally as early as the ninth month, and ends towards the close of the second year. 

2 This must not be confounded with the epipteric bone, which sometimes occupies 
approximately the same position (cf. infraj pp. 69 and 61). 

' This is also known as the os transversum, triquetum, epactale, Goetheanum, 
and most commonly as the os Incae, because of its frequent occurrence in the skulls of 
the ancient Peruvians {i.e. 5 to 6 per cent, as compared with but 1 to 2 per cent in 
European skulls). A somewhat similar " praeinterparietal " lying in front of this, 
and which wiU be described later, occurs in about 1 per cent of all cases. 



56 



THE STRUCTURE OF MAN 



between the parietals, assuming a markedly angular form {i.p. 
Fig. 38, A). Although this bone persists differently in diflTerent 
races, it is formed in the embryo firom two distinct ossific centres, 



A 




8.0. 




8.0. 




I) 





e.o. 



Fig. 38. — A to C, Various Forms of the os Incae (interparietal bone). 
D, E, Diagram of the Bones of the Occipital Region in the Embryo. 

(Partly after Ficalbi.) 
?'.;9., interparietal ; j'./>.jo., praeinterparietal ; f . o. , exoccipital ; 5.0., supra-occipital; 5. o., 

basioccipital ; f.m., foramen niagimm. 

which, at a later stage, normally unite to form one mass with the 
supra-occipital. This fact testifies to its paired nature, and, as 
in the new-born child it is still separated by a cleft on each 



THE SKELETON 67 

side of the median line from the adjacent and originally cartila- 
ginous supra-occipital, it may perhaps have existed in the ancestors 
of man as an independent bone.^ 

The interparietals first appear in Mammals, but among the 
higher forms they are seen in a state of apparent degeneration, as 
would appear from their great variability in occurrence, form, and 
detailed relationships. They may, for example, remain either 
partly or wholly isolated ; they may be either single, bilaterally 
symmetrical, or asymmetrical, or may be represented by but one 
lateral bone. 

Other inconstant ossific nuclei of this region are the prsein- 
terparietalia. These may remain partly or wholly isolated, and 
show in form and position variations similar to those above 
described for the interparietals. The possible combinations of 
these anomalous bones cannot be discussed here (cf Fig. 38). 

The morphology of the praeinterparietals is not clear, and it 
is by no means unlikely that, like the ossa Wormiana (o. suturaria), 
they fall under the category of accessory ossicles. The problem is 
rendered still more difficult by the fact that, so far as is known, 
they are constantly present only in the Horses, while in other 
Mammals they are of mere sporadic occurrence. In Man, as 
compared with the latter, they appear comparatively frequently 
(i.e. 1 per cent). Equally uncertain is the morphology of the 
OS fronto-parietale [os antiepilepticum of the ancients], a bone 
which occurs very rarely in Man, in the neighbourhood of the 
fronto-parietal suture. This bone, which is more often found in 
the Cebidae among Monkeys, and less frequently in Kodents, may 
be sometimes paired. 

An atavistic significance may be probably attached to a 
bony process which occasionally appears in Man, behind and 
externally to the jugular foramen, and into which the rectus 
capitis lateralis muscle is inserted. This corresponds with the 
par-occipital or paramastoid processus of many Mammals, which 
attains its strongest developmiftnt in Ungulates and Kodents. 

There is one more point worth consideration in the occipital 
region, i.e. the median portion of the linea nuchas superior.^ 
A bony ridge (torus occipitalis), stretching at times as far as the 
linea nuchae suprema, occasionally develops here. According to 

^ Welcker regards all the larger bones which are occasionally intercalated in 
the lambdoidal suture as fragments of the os Incae. 

^ It is difficult to decide whether the furrow or pit (fossette vermienne, 
Albrecht), sometimes formed for the reception of the vermis cerebelli, has any 
phylogenetic significance. 



58 THE STRUCTURE OF MAN 

Ecker, this ridge is common in certain races, and it is said to be 
homologous with the massive occipital crest of the Apes.^ 

In the normal adult skull the sphenoid appears as a 
single mass, and at a certain age this fuses still further with 
the basioccipital bone. A comparative study of the Mam- 
malian skull, as also an examination of the skull of the 
human embryo, however, shows that the apparently single 
sphenoid represents a series of fused bones. The basal elements 
of the skull are segmentally arranged ; but comparison 
with the lower vertebrata shows that this is a secondary 
feature in no way indicative of original metamerism. The 
cranial " segments " are no part of a primordial segmentation 
corresponding with the embryonic somites, as has been clearly 
shown by Van Wijhe and Froriep from the study of develop- 
ment (cf. infra). 

Comparative Anatomy shows us that the orbital and temporal 
fossae were originally one (as they still are even among Lemurs). 
In the human embryo, and even in the new-born child, this fact is 
still indicated by the greater width of the spheno-maxillary fissure, 
the ultimate limitation of which, by extension and the final meet- 
ing of the alisphenoid and the zygoma (malar), is not then 
effected. Before this occurs the frontal and the malar have 
already come into close apposition, and in the double relation of 
the latter to the frontal bone on the one hand and the sphenoid 
on the other, we have a distinctive character of the Primates as 
opposed to all other Mammals. We find, accordingly, that these 
connections are formed very late in the development of Man, as 
compared with the relations of the malar to the maxillary and 
temporal bones, which are established much earlier ontogenetically, 
as they were phylogenetically. 

Under ordinary circumstances, the upper edge of the ala 
magna of the sphenoid (alisphenoid) reaches the anterior lower 
angle of the parietal, but in rare cases (about 1 per cent of 
European skulls) this junction is prevented by the anterior edge 
of the temporal bone sending out a process to meet the frontal. 

^ [In the Gorilla the sagittal and lambdoidal crests attain so great a develop- 
ment in the male as to give the skull a carnivorous aspect. This feature is an 
accompaniment of the greater development of the temporal jaw-muscles ; and it 
is not acquired by the female. So marked is this sexual difference between the skulls 
of these animals that had they been first found in the fossil state, they would in the 
highest degree of probability have been regarded as at least specifically distinct. We 
have here a most instructive example of an adaptive and secondarily acquired 
character.] 



THE SKELETON 



59 



This so-called processus frontalis is remarkable on account of its 
more frequent occurrence in the lower races, such as Negroes, 
Australians, and Veddahs (according to the Sarasins it occurs in 




Pig. 39.— Skull of a Girl two years old, in which the temporal bone {tp.) is 
separated from the frontal {/r. ) by the broad ala magna of the sphenoid (alisphenoid 
bone, a.s.) ; pa., parietal. 




Fig. 40. — Skull op an Aboriginal Australian, in which the temporal bone is 
separated from the frontal merely by a long process of the alisphenoid (a.s.). 



10. per cent of the last named). This process is also often found 
in the lower Mammals. [The upper edge of the alisphenoid, above 
alluded to, may be not infrequently replaced by a distinct bone 
(the epipteric of Flower before mentioned — cf. p. 55, footnote, and 



60 THE STRUCTURE OF MAN 

Fig. 41, f). Thomson, from the study of a large series of 
skulls, has shown good reason for regarding this as one of the 
series of Wormian bones which so often occur in this region, 
and for believing it to arise by dismemberment from either the 
alisphenoid or parietal.] ^ 

The nasal bones which, as a rule, remain distinct, sometimes 
fuse to form one bone. This occurs far more frequently in the 
lower races (Patagonians and tribes of South Africa) than in the 
higher ; and it is the more probably an atavism, since this fusion 
is normal in Apes. In the Chimpanzee it takes place as early as 
the second year. 

The lachrymals are susceptible to not a few variations, and 
very rarely an abnormal enlargement of the hamular process 
causes these bones to appear at the surface of the face, as in 
many lower Mammals (Gegenbaur). 

Many variations are to be found in the bones of the inner 
orbital wall. For example, the lachrymal bone may be altogether 
wanting, or only present in a vestigial form, so that the os planum 
(lamina papyracea) comes into direct contact with the ascending 
or nasal process of the upper jaw (premaxilla). In other cases 
the lachrymal bone may be divided into an upper and a lower 
portion by a suture, and there are other variations to which it 
and the development of the hamular process are susceptible ; it 
may be occasionally replaced by a radially disposed series of 
small bones. 

A similar division of the os planum of the ethmo-turbinal 
into several pieces has been observed (Turner, Macalister, Arthur 
Thomson) ; but it is questionable if any morphological signi- 
ficance is to be attached to these variations. 

According to the cousins Sarasin, a lower stage of develop- 
ment is shown in the skulls of the Veddahs and others, in the 
downward prolongation of the nasal portion of the frontal bones 
into the orbits, which lie very close together and are spacious, 

^ [{Jour. Anat. and Phys.j vol. xxiv. p. 356). I have elsewhere pointed out {ibid., 
vol. xxiv. p. xviii. ) that the ossa pneinterparietalia lie within the area normal to the 
parietals, and that therefore these, at least, among the intercalary elements of the 
cranium, may be similarly referred to an origin from those bones, by dismemberment, 
under the expansion of the brain case. The phenomenon appears to me akin to that 
of the well-known double ossification of the supra-occipital in its most expanded 
form (ex. Cetacea and some Insectivora), and of the occasional duplication of the 
lachrymal, and of the os planum, itself already intercalated in the orbital wall in 
the Primates. (My friend Dr. Forsyth Major has lately shown me that the Lemurs 
do not differ from the higher Primates in the absence of the latter character, as is 
generally believed), — G. B. H.] 



THE SKELETON 61 

with strong, over-arching, superciliary ridges. This may be 
carried so far that the fronto-nasal suture may lie almost on 
a level with the centre of the orbit, whereas, as a rule, it lies 
much higher. The arrangement manifestly involves the frontal 
in a far greater share of the orbital wall than is the case with 
Europeans ; and, correlatively, the os planimi is in this race some- 
what more than 2 mm. narrower than that of the European. 

The bridge of the nose in the Veddahs is not nearly so high 
as in Europeans, i,e. it remains sunk between the orbits. In 
other words, the two nasal bones do not slope outwards against 
one another as they do in Europeans (in profile, they together 




Fig. 41. — The Skull of a Negro Eunuch, in which the process of the alisphenoid 
(of. Fig. 40) is represented by a distinct bone — the epipteric (f). 

describe a curve slightly concave anteriorly), and this, in life, 
results in a flat nose. This condition is palingenetically repro- 
duced in the European child, and finds its expression in the 
flatness of the nose, the bridge developing only in later years. 
The choanse of the Veddah's skull are, on an average, half a 
centimetre lower than in the European. 

Turning now to the facial portion of the skull the upper 
jaw first claims attention. That portion of it which carries the 
incisors is particularly interesting, because Ontogeny teaches that 
it was originally a separate bone, homologous with the pre- or 
intermaxillary of the lower Vertebrata. This bone is an inherit- 
ance which reappears with the greatest constancy from the bony 
Fishes upwards throughout the Vertebrata ; but whereas in by far 
the greater number of these the premaxillary remains an 
independent bone, in Primates it early fuses with the adjacent 
elements of the upper jaw to form one mass. In Man this fusion 



62 



THE STRUCTURE OF MAN 



usually occurs soon after birth ; in most Apes, on the contrary, 
much later. In Man the fusion first involves the facial portion 




Fig. 42. — Skull of a Tdrco, in which the temporal bone nearly reaches the 
frontal. Between the two a narrow process of the parietal is intercalcated. 




FiQ, 43. — Skull of a two-ykar-old Chimpanike, in which the temporal bone 
is to a considerable extent in apposition with the firontal (^r.)- 

of the bone, its palat^U part remaining for a long time, or even 
permanently, marked off from that of the maxillary by a suture 
or trace of a suture. The same is the case with the Anthropoids. 



THE SKELETON 63 

Only very rarely — and then, as a rule, in the lower races of 
mankiDd (Negroes and Australian aborigines) — does it remain 
distinct throughout its whole extent in later years, in otherwise 
normal skulls. The striking manner in which the original 
independence of the premaxillary bones is shown in people 
affected with the deformity known as hare-lip is well known: 

The number of incisora connected with the premaxillary will he con- 
Bidered later in dealing with the buccal cavity. It may here, however, 
be remarked that Comparative Anatomy affords no explanation of the double 
nature ascribed by Albrecht to each half of the human intermaxillary bone. 

Quite recently Waldeyer has drawn attention to certain 
peculiarities of the hard palate, i.e. variations in the posterior 




Pio. 4*. — Thb Hard Palatb, A, of a Cadcasian ; B, or the Neobo ; C, of an Aduli 
Obanq-Utah. Showing iirn diSereuoes in ehape of the bones. The pdate of the 
N^ro repreaentg a, type tcansittoDal between that of the Caucsaiui and that of the 

nasal spine, which had previously escaped recognition, and I 
have confirmed his observations. This spine (Fig. 44) is deriva- 
tive of the horizontal plates of the palatine bones (pi), and is thus 
morphologically paired. Not infrequently a more or less marked 
double spine is found, and where this is most evident the hori- 
zontal plates of the palatines may sometimes not even meet in 
the middle line. In the latter case the palatine processes of the 
maxillse may run back along opposite sides of the middle line, so 
as to take part in the formation of the posterior edge of the hard 
palate. These deviations from the normal arrangement have 
been observed in the skulls of Men and Gorillaa 

There are further interesting variations in the relative 
poeitions of the palatine bone and the palatine process of the 



64 THE STRUCTURE OF MAN 

maxillary,. and also in the relation of the former to the posterior 
edge of the hard palate. 

As a rule, the transverse palatine suture runs right across 
the palate, i.e. the two horizontal plates of the palatine bones 
have a more or less straight anterior edge (Fig. 44, A). Not 
infrequently, however, the median portions of these plates are 
more prolonged anteriorly, the course of the transverse palatine 
suture being correspondingly irregularly oblique on either side, as 
depicted in Fig. 44, B. 

I find the latter condition to be still more marked in the 
Orang-Utan (Fig. 44, C), and the same may be true, as Waldeyer 
has already shown, of other Mammals. [By analogy to the lower 
vertebrata] we have here an index of a low grade of organisation. 

The proximal end of the first visceral skeletal arch (Mockers 
cartilage) (I, m^^, Fig. 45), which developmen tally precedes the 
bony lower jaw (md.)} is continued into the middle auditory 
chamber of the embryo as a cartilaginous enlargement. Tliis 
becomes twice constricted to form the incus {in.) and the malleus 
(mZ.) Some authorities homologise these with the quadrate 
and articular elements of the mandible of the lower Vertebrata, 
[but according to others they are structures sui generis distinct 
in origin from the embryonic lower jaw. The value of these 
elements is one of the most vexed problems in comparative 
morphology. All investigators are, however, agreed that they 
are the representatives of an apparatus, at least in part functional 
in lower Vertebrates, in effecting the indirect articulation of the 
jaw apparatus upon the skull, and that in Man and the Mammals, 
in which this articulation has become direct, this apparatus, imder 
associated change of fimction, has entered secondarily into con- 
nection with the organ of hearing] (cf. Figs. 45 and 46). 

A trace of the embryonic connection between the malleus 
and Meckel's cartilage is long retained, in the so-called processus 
gracilis of the malleus, which passes towards the lower jaw 

^ The prognathous type of skull has been assumed to be reversionary to a pithe- 
coid condition ; but this consideration is by no means a simple one. The cousins 
Sarasin have pointed out that the lowest forms of human skulls, e.g. those of 
Veddahs, Andaman Islanders, and Bushmen, are of the orthognathous or (Andaman 
Islanders^ mesopnathous type. The orthognathous type may thus have been 
attained by human beings at a very early i»eriod, and subsequently lost. If this be 
the case (but it is doubtful) the prognathous condition of Negroes and Melanesians, 
and the gr^at projection of the jaw in some woolly and straight-haired races, must 
be a secondary condition, which has been preceded by orthognathy. In this case 
the orthognathy once more attaineii by Europeans must be regarded as a third 
jUiylogenetic phase in the evolution of the skull (Sarasin^. 



THE SKELETON 65 

through [an interspace between the elements of the auditory 
region of the skull, known as] the Glaserian fiseure. 

The second visceral or primitive skeletal arch (II, Fig. 45) 
becomes, in Man, proxinially connected with the auditory capsule ; 
distally it becomes related to the next arch behind (III o^ Fig.). 
Its intervening portion, which at first is cartilaginous, may 
become partly or altogether ossified, but it is usually transformed 




Fio, 45.— Head op a Human Emi 
anditory ossicles, tympBDic ri 
appaTstns. All tliese parts a: 

ml., malleus; in., iDcua; at., stapes 



E FuuBTH Month. Dissected to show the 
ind Meckel's eartilsge, with the hyoid and thyroid 
Jineated on a larger scale than the rest of thesltuU. 
a., tympanic ring ; tp., tympanum ; I (mk, ), first 



skeletal (mandibular) areli (Meckel'a cartilage) ; II, se.-ond skeletal (hyoid) a 
III, third (first brouchial) arch; IV, V, fourth and fifth arches (thyroid cartilage)! 
b.hg., bosihyal element ; ir., trachea ; sid., bony mandible. 

along the greater part of its length into a fibrous band. 
In other cases it is replaced by a series of small cartilaginous 
or osseous bodies which form a chain, recalling the arrangement 
existing in many lower Mammals. The proximal end of 
this arch becomes, in Man, the very variable styloid process of 
the temporal bone ; the distal end, on the other hand, forms the 
lesser cornu of the hyoid. This latter bone (the hyoid) also con- 
sists of a central portion or body {h.hy.), and a larger or posterior 



66 THE STRUCTUBE OF MAN 

comu (III), which is paired and projects there&om backwards. 
The body may be regarded as the basal element of the second and 
third embryonic skeletal arehes,' while the posterior coraua repre- 
sent the lateral elements of the third (or first branchial) areh 
alone (c£ Figs. 45, 46, and lOT). 

In the earliest stages of the embryo, the ridge which will 
afterwards develop into the second or hyoid \-isceral areh, sends 
a process backwards, which covers a deep groove (the cervical 
groove) on the postero-lateral edge of the cephalic region. The 
third and fourth branchial arehes lie in the hollow thus 
formed, and they gradually cease to be externally evident. 
The entrance to this cervical groove is bounded by the hyoid 




Fia. 48.— Skull of a Tailed Ahfbibiah {Mmoptmui). The skeletal arches tire , ^ 
lettered seriall; witL tLose of Mau, in Figs. 45 ond -MS. " n 

gu., quadrate cartilage ; ar., articular end of mfe, Meckel's cartilage ; I, mandiliular 
arch ; II, hyoid arch ; III, IV, V, VI, branchial skeletal arches. 

arch ; and there can be little doubt that we have in the above- 
mentioned ridge a feeble homologue of the gill-cover of fishes 
and metamorphosing Amphibia. It at a later stage fuses with 
the adjacent body wall, the cer\"ical groove (branchial chamber 
of the Anamnia) becoming thus closed. 

The hyoid apparatus, which is intimately connected with the 
cervical, lingual, and mandibular musculature, is in fibrous con- 
nection (tbyro-hyoid ligament) with the upper edge of the 
laryngeal skeleton ; and of this skeleton the thyroid cartilage at 
least (IV, V, Fig. 45) arises from the fourth and fifth bran- 
chial arches (cf. Fig. 107 and p. 151). 

' [It in usually stated to be oasifieil from a single centre in Mammals, but the 
faot, to which my friend Mr. M. F. Woodward baa drawn my attention, tliat it may 
bo oiica«ionftlly subdivided by a transverse suture into two portions [ex. Lcpiia) 
Indicative of itn oMiillcatioD from two recurrent centres, is of much interest in this 
coiiii«:ti..ii.-0. R H.] 



THE SKELETON 



Skeleton of the Lib 



So far as the r skeleton a oncern d the f re and hind limbs 
of Men and other Verteb ates notw thstan 1 n^ their TariouB 
adaptive modifi at o ^ are u n stakallj built on the same plan. 
This fact not only find? t express n n the sir t y homologous 
segmentation of the r free po t ons but s c ntirmed by Compara- 
tive Anatomy ani OntOj,enj 

Without ente ng at length nto the old controversy as to 
the phyl(^ny of the 1 mbs I wo Id br efly lehne my own posi- 




HB EUUB A Srabs {PrUHiirut 

gi h Pecto Limb Bud (op. ) 

ck.^ noto hd^(£in mes iil}e growiug 

ventrally ; my., spinal cord. 

tion with regard to this question. I agree with Balfour and 
Dohrn in regarding the limbs of the Vertebrates as outgrowths 
of the primitive body segments, and thus believe in their originally 
segmental nature ; and I see in thia an argument for the origin 
of existing Vertebrates from segmented Invertebrate ancestors. 
In other worda, these limbs, which in origin are polymerous, 
involve phylogenetically a certain number of body segments with 
their muscles and nerves ; and these, in consequence of functional 
adaptation, must necessarily undergo different modifications in 
the different groups of Vertebmtes. Although this subject 
cannot be further diacussed here, it may be remarked, in passing, 
that the differencea between the anterior and posterior limba, 
resulting from adaptive modification, become less marked the 
lower we descend in the vertebrate series ; indeed, a starting-point 



68 



THE STRUCTURE OF MAN 



of approximate structural uniformity is finally reached among 
the Fishes. In the higher types, and especially in Birds and 
Mammals, the limbs have greatly diverged. In the former, the 
whole weight of the body is thrown on to the posterior limbs, 
which are thus purely supporting organs; and the anterior 
limbs, relieved of their original supporting functions, have 
become transformed into organs of flight. 




Fia 48. — DiAGRJkM ILLrSTRATIXG THE DSVELOPMSXT OF THE FiXS OP A FiSH. 

A, To show the first formed and origiiially continaoiis lateral (/./.) and dorsal (/.</.) 

fin-folds : /.r. indicates the point where the lateral folds are continaed rentrally 
behind the anus {a,\ 

B, To show the definitive fins [which owe their independ^ice to the absorpti<m of the 

primarily eon tinnous folds throoghont the areas iudi<^ed by the dotted lines], <r., dT. , 
dorsal fins ; pe., pectoral : pl^ ventral or (telvic fins ; r., anal ; and c candal fin. 

An almost equally advanced modification is found in many 
Mammals, e.g. Man, in whom the anterior limbs have been trans- 
formed from ambulatory into prehensile organs, the *' fore-feet " 
becoming hands. 

A detailed comparison between the upper and lower limbs of 
Man will be instituted at the close of this section ^iii/ra, p. 91). 

The Pectoral (^Shoulder) and Pelvic (Hip} Girdles 

That the limb-girdles were of later origin than the skeleton 
of the firee limbs is rendered probable by the Ontogeny of all 
Vertebrates 

The following is the couKse of developmem in the embrvo Shark : — 



A number of originally separate skeleiogeuous rivs (nrf^. Fig. 49, A), de- 
velop in the dermal fiu-foKis ^ : aiuL by fusion at their piv*ximal ends, even 
before they ai^ at all chondrifieii, they give origin to a basal plate ^fe\ The 
anterior ends of the basal plates of opfK^site sides next approximate C^Pig- 49, 
B>, and finally fuse in the midvile line, leaving passages lor their related 

^ [Grvat iniexetst attaches to the iwvnt di^tLX^vy^ry, that in the F^UxoBoic Selachian 
Cia<i<^Mckf. th«Ese nys retained their (^nnMunr iikde|>«ndeiiee in the adult pelvic 
fin. Of. IVan, J^^r. M^vyik., w>i, ix. p» $7.] 



THE SKELETON 69 

DeTvea. Of the cartilaginous arch thus fomied, the middle portion becomes 
in the fore-limb the pectoral, and in the hind the pelvic girdle, and both of 
these mast therefore be regarded as products of the skeleto^enous blastema 
of the free limbs. The segmentation into a central girdle and lateral 
limb supports is effected by a process of resorption (cf. ffig' 49, C), the 
points at which this is effected becoming the shoulder and hip- joints. 




FjO. 49.— A, B, C, DiAORASIMATIC RePBESESTATIOK OF THBBE SCCCESSIVE SlAOES 

IM THE Development op the Pki.vic Fins of a Shark. 
rd., primitive skeletogeaous raya ; Id A t1i«sfl are alrettcly commencing to grow together to 
form a basal plate (bi.) ; in B this fnaton has taken place oil botli aides, and at * 
the proiinial ends of the basal plates are approiimnting to form the limb girdle ; 
In C the process is cnmpleteil, and at + the free limb akeleton ia being constrinted 
off. The formation of secondary rays at the periphery is deUiieated to the left of 
C [ figure /o.p foramen obturatorium ; cl,, cloaciil aperture. 

It would appear from the foregoing that not only the girdles, but also 
the basal limb supports which articulate with them (the later femur or 
humerus), were primarily the products of fusion of parallel rays. Inasmuch 
as this consideration, as will appear later, is of profound importance in 
dealing with the morphological significance of the limbs, this brief digression 
into Embryology has been unavoidable. Fig. 50 further illustrates the same 
subject, showing the probable manner in which the number of skeletal rays 
which unite to form the limbs of terrestrial Vertebrates ia reduced. 



THE STRUCTURE OF MAN 




B Limbs of Tkrbesthul Vbrtb- 
jvKD, BY Modification, 

FHCM THE Fl>S OF FlSHBS 

The shaded parts indioiite raja vfhich atrophy; A, pelvic fin of a Sturgeon; B, 
diagram of the posterior limb of a lurvi^ Salamanrier ; C, tlis hinil limb of 
an adult Urodele Amphiljian {Ranodon) ; p., pelvis; bi., basale (femur); rd'., 
proiimal rajs (tibia, iibuls) , rp, ]>eripheral ray segments (tarsal aod other 
elements of the pedal skeleton) rd '. , isy» which atrophy and ultimately 
disappear 



THE SKELETON 71 

Phylogenetically, the oldest elementa of the pectoral girdle 
are the scapula and coracoid, and of the pelvic girdle the 
ischium and pubis ; for though in certain Fishes the clavicle and 
the ilium are indicated, they are only fully developed from 
the Amphibia upwards. 

Fig. 51 is the ventral view of the pectoral girdle of a 
tailed Amphibian. It shows that the clavicles (cl.) are directed 
forwards (i.e. towards the head), and that the coracoids (co.) 
overlap each other ventrally. The edges of the latter, which 
are connected by fibrous tissue, only loosely overlie the small 
so-called "sterilum" {st). The connection between the coracoids 




Fin. 51. — Pbotobal Girdle of a Tailed Ahphibias, from the 

Vknthal Side. 

d,, clavicle ; co., coracoid ; nr,, shoulder-joint ; s(., so-called "sternum." 

1 the sternum becomes much closer in E«ptiles and Birds, and 
the lowest Mammals. The withdrawal from this 
connection seen in the higher Mammalia is proportionate to the 
greater development of the antero- ventral element of the pectoral 
girdle, the elavicla Through the mediation of this bone the 
scapula finds a new support upon the sternum, and thus the limb, 
being the farther removed from the trunk, attains far greater 
fi'eedom of movement. 

The expanded coracoid of the lower Vertebrata is, in Man, 
represented by an apparent process of the upper edge of the 
scapula, called the processus coracoideus (co.. Fig. 52). This serves 
as a point of origin and attachment for certain ligaments and 




72 THE STRUCTURE OF MAN 

muscles, but its original independence and greater significance is 

seen in the fact that it ossifies from two distinct centres, which 

in Man only completely fuse with one another and with the 

bony scapula after the sixteenth to the eighteenth year. [This 

double ossification of the eoracoid occurs only in Mammals 

among living Vertebrates. The overhanging portion of the 

coracoidal region of the human blade-bone, which (eo., Fig. 

52) from its suggestiveness of a bird's head has been termed 

the "eoracoid process," answers in 

every detail of relationship to the 

epicoracoid of the lowest Mammals 

(e.c.. Fig. 28). The basal portion, or 

second coracoidal element (which 

does not appear in the human suh- 

■, ject until the fourteenth or fifteenth 

year), represents, in a highly reduced 

and vestigial condition, the more 

robust element of the Omithorhyn- 

chns eoracoid (m.c., Fig. 28). It was 

Fio. 52.-Ri.HT Bl^eB>-<e op a >^°*»1 recently known as the "cora- 

New-bors Child seek thom the coid"; but, as it and the epicoracoid 

INNER OR Costal Suhfacf together represent the entire eoracoid 

CO., coracDid process ; the dark spot ° ^ 

atM. represents the first of its two of the lower Vertebrata, the term 
™ntresofossifioation;ar.,articular metacoracoid is now applied to it.y 

facet tor humerus ; sc, scapuls. » '^ -" 

The scapula is in Man a broad 
bone, its form being doubtless attained in functional adaptation to 
a very strongly developed shoulder musculature. In those lower 
animals, in which the anterior limbs are simple ambulatory organs 
performing leas complicated movements, the scapula is not so broad, 
especially at its median and hinder border — the so-called base. It 
is therefore very interesting to be able to prove, both by the 
Anatomy of the lower races (Negroes and aborigines of Australia) 
and by human Ontogeny, that the great breadth of the median 
part of the human scapula, and the sharper differentiation of its 
spine, may both be considered as secondarily acquired features, 
which stand in direct relation to the gradually increasing func- 
tional activity of the fore-limb.^ 

• [Cf. Ljndekker and Howes, Proc. Zool. Soc., Lond. 1893, pp. 172 and 585.] 

* [The scapula of the higher Mammalia dilTers moat conspicuously from that of 
the lowest Mammals and all lower Vertebrates, in its expansion, cephalad of its spine, 
to form the so-called prestapular lamina. This is but feebly fonned in Man. It 
attains ita highest development in association ivith marked specialisation of the 
fore-limb— not, however, always for the same purpose. This is readily seen, for 



THE SKELETON 73 

The close connection between the increased efficiency of 
the fore-limbs and the stronger development of the clavicle 
has already been pointed out; and the great physiological 
significance of the clavicle is further shown by the fact, that 
at a certain stage in development it is the strongest por- 
tion of the whole human skeleton and the first to become 
ossified.^ 

One distinction between the shoulder and the pelvic 
girdle, evident even on superficial comparison, lies in the more 
limited capacity of movement of the latter, which is in turn 
associated with the more limited movements of the hind-limbs. 
But although mechanical causes, connected with the upright 
mode of progression, certainly play a great part in determining 
the condition of the latter, they do not furnish the complete 
explanation, as a similar immobility of the pelvis is found 
in the lowest terrestrial Vertebrates, Eeptiles, and Amphibians. 
And further, as in both of these, and especially in the tailed 
Amphibians, no great distinction is found between the mobility 
of the anterior and the posterior limbs, the first cause of the 
distinction so marked in Man must therefore be sought elsewhere. 
It seems to ine to lie, on the one hand, in functional adaptation 
of the pelvis to the requirements of reproduction, and on the 
other, in the fact that the distal part of the pelvis forms the 
functional posterior end of the trunk. At this part of the body, 
where the posterior apertures of the urinogenital and alimentary 
systems occur, a firm framework is needed for the related con- 
vergent viscera. Such a framework would be a predisposing 
factor in the development of the powerful sphincter and limb 
muscles, furnishing the latter with a more extensive and firmer 
surface of attachment, which could further be turned to account 
by the free posterior limbs. 

The relationships of the pectoral and pelvic girdles to the 
vertebral column are essentially alike in principle. In neither 
case, among terrestrial Vertebrates, is the connection attained 
directly, but always through the intervention of ribs. The 

example, on comparison of the Sea Lion {Otaria) and Great Ant- Eater {Myrmeco- 
phaga)^ in the former of which the prescapular lamina far exceeds in area the rest of 
the blade-bone. The Sea Lion uses its fore-limb as a swimming organ, the Ant-Eater 
for tearing up Termites' nests and digging.] 

^ In the scapula of the Veddahs, the greater slant of the spine towards the 
posterior edge, and the consequent greater development of the suj)raspinous fossa 
(prescapular lamina) as compared with that of Europeans, may be indicated as 
primitive features (Sarasins). 



74 THE STRUCTURE OF IVIAN 

shoulder girdle is loosely attached to its ribs by muscles, the 
pelvic by firm ligaments and a definite articulation.^ 

In the human embryo, as in all living Eeptiles, Birds, and 
Mammals, the embryonic pelvis is triradiate, its cellular blastema 
at first forming one mass with that of the developing femur : this 
condition I have traced through the whole series of Vertebrates.^ 
After the pelvic blastema has, at a later stage, become differ- 
entiated from that of the femur, which is the first to become 
cartilaginous, the ilium, ischium, and pubis are laid down as 
distinct chondrifications. The fusion of the acetabular portion 
of these three pelvic cartilages takes place in the following 
order : first, the ischium alone unites with the ilium, and later, 
the ilium with the pubis. The ischium and the pubis do not 
send out acetabular processes towards one another, and for this 
reason a space is left at their point of apposition. 

[The bone to which in the adult human subject the term 
pubis was first applied, is formed by the union of two distinct ele- 
ments — a main one arising in utero, and a lesser, arising during 
the thirteenth year ^ within the acetabular region, and completely 
excluding its neighbour from that cavity. The latter element 
is of regular occurrence among the lower Mammalia, and being 
in them of considerable proportions has received the name 
" cotyloid bone " or " os acetabuli." In accordance, however, with 
its ultimate fate, it may be more appropriately termed the 
dorso-pubic element, and its neighbour the ventro-pubic.^ Thus 
considered, comparison of the pubis with the coracoid (ante, 
p. 72) shows that in Mammals, and in them alone among living 
Vertebrates, each consists of two elements, of which one 
(epicoracoid and pre - pubic element) is excluded from the 
articular facet (glenoid cavity and acetabulum).] 

In no other Mammals do the iliac bones diverge so greatly 

^ This difference appears less marked, and may altogether vanish, when we 
compare the [lower vertebrata. Among Chelonians the shoulder girdle very generally 
articulates upon the anterior thoracic vertebrae ; and in] Fishes a firm connection 
is established between the shoulder girdle and the skull (Osteichthyes), or even 
between the fonner and the vertebral column (Rays), [such as is seen also in many 
Frogs and Toads, and may, under rare conditions, occur in Man himself.] In 
certain Salamanders we find, on the rib approximate to the inner border of the 
suprascapular, a plate-like cartilaginous expansion, which is fastened to the shoulder 
girdle by means of ligaments ; [this, however, has probably to do with protection of 
an adjacent pulsatile "lymph -heart."] 

'^ The author here refers in the original German to his ** OlUdmassen Skelet der 
Wirhelthiere," Jena, 1892. 

3 [Cf. Krause, Month, Internat. Jour. AncU. and ITist.y vol. ii. p. 160.] 

* [Cf. Howes, Jour. Anat. and Phys., vol. xxvii. p. 650.] 



THE SKELETON 76 

as in the higher races of Men. This feature is not, however, 
marked during fcetal Ufe, when the form of the pelvis recalls 
that found in the adults of the lower races ot Men and in the 
Apea.' The whole embryonic pelvis is tompdrati\ ely long and 
narrow ; its angle of inclination is much greater than in the 




Fig. 53. — Pelvis of a FBsiiLE Chisipanzbe, 

'.a, sbctbI ribs ; ac,, acetabnlum ; f.o., obtumtor foramen ; 

pabis ; pb,, pubis ; il., iliiim. 



., sjmpUj-sii 



adult, and the long axis of the sjTnphysis pubis forms anteriorly 
with the axial line of the body a veiy acute angle. We herein 
meet with a form of sacrum resembling that of lower Mammals, 
and a promontory which only slightly projects (cf. Fig. 53). 
As a consequence, the entrance to the pelvis is also like that of 
the lower Mammals, and differs greatly from that of the later 
adult foi-m. 

' The pelvis of tlie Veddab, according 
European in its relative length and 



> the SarasiLis, dilTora from that of the 



76 THE STRUCTURE OF MAN 

The close connection between the great expansion of the 
iliac bones and the upright gait of Man has already been pointed 
out {ante, p. 38). 

The sexual dimorphism of the pelvis is more marked in Man- 
kind than in any other Vertebrate ; indeed, it may be considered 
as a characteristic of the human species, the rationale of which 
has still to be discussed. 

If we consider the marked lateral projection of the iliac bones 
which is met with in both sexes, and has already been described 
and accounted for, it seems natural enough to regard their in- 
creased expansion in the female as an adaptation to sexual re- 
quirements. This increase of breadth is the more necessary, 
since the human embryo attains a higher development before 
birth than do the embryos of most Mammals, the skull and brain 
being incomparably larger in proportion to the size of the mother. 
So highly differentiated an embryo, again, must influence the pelvic 
aperture, and, indeed, the whole form of the lower parts, includ- 
ing the promontory, since the pressure of the pregnant uterus is 
not exerted ventrally as in Quadrupeds, but, on account of the 
upright gait, sagittally. The iliac wings thus play the chief part 
in carrying this weight, and naturally undergo a corresponding 
lateral plate-like expansion. Further investigation concerning the 
pelvis in relation to " labour " in the different races of Mankind 
would be of great interest. All that can now be stated with 
certainty is, that sexual differentiation of the pelvis, at least so 
far as the expansion of the iliac bones is concerned, is much 
less marked in the lower than in the higher races. 

The Skeleton of the Fbee Limbs 

As already indicated, the fore- and hind-limbs of Man con- 
form to a single type ; and any doubt which might exist as to the 
differences between the two having been secondarily acquired by 
functional adaptation, is dispelled by Comparative Anatomy and 
Ontogeny. As already pointed out (pp. 68, 69), a review of the 
various groups of Vertebrata shows that the farther we go back 
in the series the less marked are the differences between the fore- 
and hind-limbs ; until at length, in the Fishes, we have an undif- 
ferentiated starting-point for the two. At the top of the scale 
we have the Birds with their fore-limbs metamorphosed into wings 
(under conditions by which the pelvis and vertebral column 
become correlatively modified with the hind-limbs, to support the 



THE SKELETON 



weight of the body) ; and Man, with what was originally a fore- 
foot turned into a hand. 

Before trying to answer the question aa to the mode of 
origin and progress of these important differentiations, let us 
consider the structural variations to which the free limbs are 
susceptible. 

The free limLe undergo greater and more numerous modi fi cations than 
their related girdles ; and the probability that this may be perhaps connected 
with their exposed position and intimate contact with the environment, may 
be worth consideration. 



The Skeleton of the Fore- Limb 

The fore-limb of the Anthropoids is relatively longer than 
that of Man, and it is therefore specially interesting to note that 
in some of the lower races of Men the arms are relatively much 
longer than in Europeans. In the Veddahs this difference is 
even externally obvious, and when the skeleton is examined, is 
seen to be, as in the Anthropoids, chiefly due to the great 
length of the forearm (radius and ulna). If 
the length of the humerus be taken at 100, 
that of the radius is 73 in the male European, 
nearly 80 in the male Veddah, and 90 to 94 
in the Chimpanzee (Sarasins). This great 
development of the forearm is distinct Ij a 
mark of low organisation, and it is a si^nifa 
cant fact that it obtains in the Eui-opean foetus 
and child, only giving place to the definitive 
proportion with advancing age. (Similar 
variation with age is found in the fore leg cf 
infra.) 

The occasional perforation of the olecranon 
fossa of the humerus, to form what is known 
as the ent-epieoudylar (supra-trnchlear) foiamen 
(Fig. 55), is undoubtedly to be regarded is 
atavistic. It is often found in the lower races 
of mankind, e.g. natives of South Africa and Fia 54— Right Hum 
has been observed in the Veddahs in a** many snoniho PerfohT 
as 58 per cent, in skeletons belonging to the *''0'' °^ f"E Olb 
stone-age, in the Anthropoids (Gorilla and termor ipJa"* 
Orang), and in the lower Apes. 

On the ulnar side of the lower end of the humerus, a few 




THE STRUCTURE OF MAN 



centimetres above the internal condyle, a bony process (processus 
aupra-eondyloideus) (pr., Fig. 65, D) sometimes projects in a hook- 
like manner, a fibrous band passing from it to the ent-epicondylar 
region. The Median Ner\'e runs through the foramen thus 
enclosed. This foramen is very common among the lower animals. 




Fio. 5E. — Distal Extbbuiti of the Huueritb to show Epicondylar Fohahika. 
A, in HatttHa : B, Id b Lizard {LaeeHa ocdiata) ; C, in the domeatic Cat ; D, in Man ; 
e.e,, external condyle ; c.i., internal condyle. In A tbe two foraniina are dereloped 
{at i, the ent-epicondyloT ; at il. the" ect-vpicondjlar). The only cnn&l (f ) present 
in the Lizard (B) is on the eiternal volar aide, in the cartilaginous dlstai eitrmnitj. 
la Man (D) an ent-vpieondylar process (pr.) is developed and continned aa a fibrous 

and is of very great antiquity. It is found not only in very many 
quadrupedal Mammals, but in Eeptiles (Fig. 55, A and E), in 
fossil forms which skeletally combine Amphibian with Beptilian 
characters {FcUwokaiieria, Jlomwosaurns), and in fossil Amphibians 
(Stegocephala) of the Permian period (Stereorhachis and Both- 
riops)} 

' [Stnithera lias recorded an interesting case of hereditary development of this 
supra-coiidyloid process {Laiuxt, 15tli February 1873). and bos specially advocated 
the view that tlie completioD of the process in Man has a reversionary significance, 
and not that of mere overgrowth for protection, frequently occnrrent in all parts 



THE SKELETON 79 

In the great majority of Keptiles a similar aperture (ect- 
epicondylar foramen) is found on the outer side of the humerus, 
(Fig. 55, A ii), and in some both foramina are present. These 
are in both cases nerve canals, which fact suggests that they may 
not have arisen either among Amphibians or Eeptiles, but rather 
among animal forms phylogenetically still older. 

[In consideration of the facts already recapitulated (pp. 68-70) con- 
cerning the comparative anatomy and development of the vertebrate limb- 
skeleton, the probability that these condylar foramina may be indicative of 
a] polymeric origin of the basal segments of the limb-skeleton must not be 
overlooked, for, in the Ontogeny of the Sharks and Sturgeons, these latter can 
be traced to an origin by concrescence from pamllel cartilaginous rays. If this 
be the meaning of the foramina, the fact that among living Reptiles they are 
most marked in the most primitive genus (Hatteria) is the more interesting. 

I have elsewhere ^ raised the question whether the foramina nutritia, 
occurring in the long bones of the limbs, may not have had a similar origin. 
A wide field is here open for research, in which palaeontology should play an 
important part. 

Special interest attaches to the skelett)n of the human hand, 
and there is still abundant room for 
further investigation concerning it. 

Taking first the carpus, the re- 
semblance of that of Man to the 
carpus and tarsus of the tailed Am- 
phibians is most striking. In its 
proximal row there are the three well- 
known bones, the radiale (scaphoid = 
tibiale in the pes), the intermedium 
(lunar), and the ulnare (cuneiform = 
fibulare in the pes), cf. Figs. 56, 57, 
59, 60. In the distal row, counting 
from the inner or radial face, lie the 
first carpale (trapezimu = 1st tarsal or 

• n ..1 N^i r»i Fig. 56.— Skeleton OF THE HiND- 

ento-CUneiform m the pes); the 2nd car- limb of a Tailed Amphibian 

pale (trapezoid = 2nd tarsale or meso- , {Spderpesfuscus). 

^t, . j^. ^/a, tibia; /6., fibula ;<., tibiale; 

cuneiform m the pes) ; the 3ra carpale /, intermedium ; /, ftbuiare ; 
(magnum = 3rd tarsale or ecto-cunei- c,^ce>itraie ; i-§, tarsaiia ; i to v, 

form in the pes) ; and the 4th carpale 

of the skeleton (cf. Rep. Intcmat. Medic. Congress^ Lond. 1881). A remarkable 
outcome of the latter tendency has been recently described by Griinbaum, in the 
discovery of a ligament which, bridging over the i)osterior condylar forauieii, forms a 
tunnel for a branch of the occipital artery, and, by ossification, may form '*a ring of 
bone projecting downwards from the lower surface of the occiput" {Jour. Anat. and 
Phys.y vol. XXV. p. 428, and Macalister, Hid. p. u'/.).] 
^ Das Gliedmasseu Skelet (see ante, p. 74, footnote). 




80 THE STRUCTUEE 01' MAN 

(=cuboid in the pes). The last-named bone (4 and 5, Fig. 57) 
gives articulation to two metacarpals, viz. the 4th and 5th, and 
its originally double natiire is thus indicated. This is shown 
(apart from comparison with the carpal skeleton of the lower 
Vertebrata) by the occasional division of this bone into two, not 
only in Man, but in the most varied Mammals (Marsupials, 
Rodents, Cetacea). 

All who are in any degree acquainted with Comparative 
Osteology, know what a great part is played by the os eentrale as 
a component of the carpus and tarsua To Gegenbanr belongs 
the honour of having first recognised and appreciated this. 
All investigations made after the year 1864 had to start from 




FlO. 57. — DlAQRAU Of THE HUMAN CaHPUS. A, EhBHYO ; B, ASULT. 

rd,, FHiiius ; u/., ulna; u, uluare (cuneironu) ; t, intern icdium (lunar); r, radiale (scaphoid); 
}i, piaiforiae ; 1, 2, 3, carpalia (ttapezium, trapezoid, and magnum) ; 4 + 6:=unit^ 
4th and 5tb carpalia (represented in tbe adnlt by a sit^le bone, tbe nneitorm) ; c, 
eentrale, whicb fuses lst«r witb the ladisle (scaphoid] ; i to v, digits. 

the broad basis laid down in his exbensive researches into the 
limb-skeleton of representatives of the chief types of terrestrial 
Vertebrata. In only one of these was Gegenbaur unable to reach 
a perfectly satisfactory conclusion, and that was in Man himself 
It was reserved for Rosenberg, ten years later, to establish the 
fact, that the eentrale in an early stage of development (i.e. at the 
beginning of the second month of intra-uterine life) is a distinct 
carpal element. By this discovery the ■ chain was completed, 
Man forming the last link. 

Rosenberg's discoveries were soon confirmed and extended by 
other anatomists, among whom may be mentioned Leboucq and 
von Bardeleben. The former proved that the centr&Ie did not 
vanish, as Rosenberg believed, i.e. it was not resorbed, hut incor- 
porated into the radiale (scaphoid) in the second half of tbe third 



THE SKELETON 81 

month of fcetal life, giving rise to a prominence which can be 
recognised in the adult. This prominence is present also in the 
Chimpanzee, the Gorilla, and Hylohates ; and as the centrale is 
most probably distinct in the embryo of these, it may well be 
that in them, as in Man, its independent existence has not long 
been suppressed. Further confirmation of this is afforded by the 
fact that it is still an independent bone in 0*4 per cent of even 
adult human beings, and that, normally, it retains its independence 
in the Orang and in most Monkeys. 

In many Mammals (especially Marsupials, Rodents, and Insectivores) 
cartilaginous or bony skeletal elements occur on the outer and inner borders 
of both fore- and hind-limbs, which not only bear a superficial resemblance 
to the digital skeleton, but may in some cases be clad, like the true digits, in 
either a claw or a callous hornv integument. Similar structures occur in 
many of the lower Vertebrates (Reptiles and Amphibians). These organs 
were formerly considered by both von Bardeleben and myself to be vestiges 
of now vanished digits, and were named by us ^^prsepollex," " prjehallux," 
and " postminimus." 

I have, however, entirely changed my opinion as to the supposed atavistic 
nature of these structures, and now agree with others that these "super- 
numerary rays," whether they occur in the lower or the higher Vertebrata, 
are to be regarded rather as progressive structures of convergent and second- 
arily adaptive significance. Baur has contended, before all others, that the 
facts of palaeontology favour the view that the terrestrial Vertebrata never 
possessed more than five rays in the skeleton of either fore- or hind-limb ; ^ 
and my own recent investigations into the development of the limb-skeleton 
entirely confirm this conclusion. 

From this point of view, the condition of *' hyperdactyly," which not 
infrequently appears in Man and is often inherited for many generations, 
loses its supposed atavistic significance. 

The Skeleton of the Hind-Limb 

The human femur usually bears at its head two processes for 
muscular attachment, known as the trochanters, inasmuch as 
they give insertion to the rotator muscles of the limb. Special 
interest centres in the not infrequent presence of a third trochanter 
(Jtc"\y Fig. 58), a development of the roughened area (tuberositas 
glutealis) which occurs on the external border of the bone 

^ [It is an interesting corollary to this, that the only fossilised limb in wliich any- 
thing comparable to a sixth digit has been found, is a fore-limb which, if not actually 
Mammalian, is that of a Reptile with ]\[ammalian characters ( Theriodesitiics, from the 
Mesozoic beds of South Africa, cf. von Bardeleben, Froc. Zool. Soc, Lond., 1889, p. 
269 ; and Seeley, Proc, Hoy, Sue, Lond., vol. Iv. p. 227). Nor must it be forgotten 
that the **pr8ehallux" in its most highly differentiated and digit-like fonn (Frogs 
and Toads) is cartilaginous, i.e. so constituted that it would not be preserved in the 
fossil state.] 

G 



THE STRUCTURE OF MAN 




in question. This third, or gluteal trochanter, may be ac- 
companied by a more or less extended ridge {cr.. Fig. 58) or by a 
pitlike depression. It is found in about 30 per cent of European 
skeletons ; ' in Negroes its occtirrence is less frequent, and in the 
Anthropoids it is still rarer 

In the Lemuroidea on the other 
hand the third trochanter is almost 
always de\ eloped- Dollo attributes 
its gradual disappearance m Man to 
certain modifications which m the 
course of time have taken place in 
the gluteus maximus muscle In the 
Lemuroids tl is muscle passes direct 
to the femur ani the development of 
a third trochanter is unquestionably 
an outcome of this association but 
in Man, the gluteus maximus is 
partially inserted into the fascia lata 
investing the superficial parts of the 
limb ; and this shifting of its attach- 
ment would appear to have led to an 
rio. 58.— Proximal half of a accompanying degeneration of the 

I«FT HOMAS FkMOB P0SSB9SBD .. ■ ■ \ \. t 

OP TBBBB Tbcwhantkhb, pos- tuircl trociianter. 

TKRioR AapBCT. In the Anthropoid Apes the 

'"■'tMrfOTginte^'Santer!' " insertion of the gluteus maximus 
into the fascia lata has gone much 
farther than in Man, i.e. this muscle has in them deviated 
farther from its original condition [in which we find it in many 
quadrupedal types], and the occurrence of the third trochanter 
is therefore much less frequent. 

The lower part of the leg (fore-leg) has, like the lower part 
of the arm (forearm), but to a far higher degree, undergone 
great -iMdifieations in length in the races of mankind. The 
variationS-B^the human tibia, indeed, are greater than those of 
any other boneSn the skeleton. Apart altogether from variation 
in length, the term platyknemia is applied to a peculiar condition 
associated with great compression of the tibia. This is found 
in the lower races, accompanied by a strong development of the 
tibialis posticus muscle, and in skeletons belonging to prehistoric 
timea 

* [Treves Ima recently called attention to a case in which it coiild be readily 
detected in the livin gpcrson (Jour. Anat. and Phya., vol. xxL p. S2&).] 



1:HE skeleton 83 

In the lower Mammals both tibia and fibula articulate with 
the femur, and contribute to the formation of the knee-joint. 
In Man, under advancing phylogenetic development, the weight 
of the body has come to rest on the tibia alone, and the proximal 
end of the fibula has become disconnected from the femur,^ 
and has shortened and shifted downwards along the postero- 
external surface of the tibia. 

The human fibula is now an appendage of the tibia, and the 
fact that its degeneration has not gone farther ^ is accounted 
for partly by its important connection with the heads of certain 
muscles of the leg (especially the peronei), and by the part which 
it plays in the formation of the ankle (external malleolus). 

The external condyle of the tibia varies very much in different 
races. In the lower races it is much more convex than in the 
higher, and this is probably also the case in the oldest prehistoric 
men. This convexity is evidently connected with the frequent 
strong flexure of the knee-joint, such as occurs in squatting. 

On the inner border of the distal extremity of the tibia 
(malleolus internus) there is, in the lower races, a special facet 
which articulates with the neck of the astragalus ; and the presence 
of this may be also connected with the strong " dorsal flexion " 
consequent on the squatting posture. The astragalo-tibial articula- 
tion thus formed rarely occurs in the higher races ; but parallel 
modifications of both the upper and lower ends of the tibia occur 
in the Anthropoids and among the lower Apes (Arthur 
Thomson). 

Until approximately the seventh month of foetal life, the 
tibial malleolus is larger than the fibular, projecting downwards 
farther than the latter. In the seventh month the two appear 
about equal, and then the fibular malleolus begins to take the lead. 
These phases of development are accompanied by corresponding 
modifications of the astragalus (Gegenbaur). 

That the earlier condition of these bones is the inherited one 
seems probable from comparison of those of the Lemuroidea, Apes, 
and lower human races. Fig. 59 illustrates the manner in 
which the external or fibular malleolus (c.f.) gradually, in adaptation 

^ [The human fibula has been stated by Leboucq, Bernays, and others, to be 
during early development in contact with the femur, from which it would appear that 
the loss of connection between the two takes place ontogenetically. Griinbaum, 
examining the parts with extreme care, has lately shown {Jour. Anat, and Phys., 
vol. xxvi. p. OCX.) that this is not the case from the period of primary differentia- 
tion of the parts in cartilage onwards.] 

' In many lower Mammals it has still further degenerated. 



84 



THE STRUCTURE OF MAN 



to the upright gait, becomes longer than the internal or tibial 
(c.t.) ; and also how the astragalus (as.) and calcaneum (cl.) which 
originally slope laterally outwards, shift inwards, i.e. towards the 
pre-axial side, so that they come more into a line with the long 
axis of the tibia. 

The above-described modifications find a parallel in certain 
most important changes which the foot itself is even now under- 
going. To understand these rightly we must enter somewhat into 
detail, in order to gain an insight into the primitive history of 
the human foot. 

Thanks to Comparative Anatomy and Development, we have 




Fia. 69.— The Upper Ahklb.Joint, Pobtkhios Aspect. 

A, adnlt Chimpanzes ; B, Australian nativa ; C, Caucasian, to sliow tbe Increasing length 
of the maUeolus flbularis (c./.), and the diEfeience in the position of the astragalus 
{as.) and calcaneum (d.) in relation to tha long aiis o( the tibia, in passing from 
the lower to the higher type. 

obtained a sufficiently correct estimate of the skeleton of the 
limbs in general, to grasp tbe essential points in the plan of 
structure common to the hand and foot. The fact that there are 
obstacles in the way of obtaining a perfectly clear insight into 
this matter need not surprise us, when we take into account the 
long series of adaptations which have resulted in the human 
limbs ; indeed, we can no longer expect to find the primitive condi- 
tion retained jn either the fore- or the hind-limb. If the fore-limb 
has been transformed from an ambulatory to a prehensile organ, 
the hind-limb has already reached a third stage in progressive 
modification — as, having first served for support and locomotion, 
it next became transformed into a grasping organ (as is proved 
by the musculature of the sole of the foot, and by the Ape-like 
apposable condition of the great toe during fcetal life), and 



THE SKELETON 85 

finallj, on the aasumption of the upright gait, it has changed 
back into an ambulatory appendage. 

This ultimate modification haa been accompanied by the greater 
development of the tarsus, and 
by the concomitant degeneration 
and decreasing mobility of the 
phalanges ; and, correlatively, the 
foot has acquired a disposition at 
a wider angle to the fore-leg, and 
has become arched in adaptation 
to its supporting function. 

These repeated changes of 
function may well have residted 
in great structural changes, 
which we may now consider in 
some detail. 

First, comparing the skeleton 
of the human foot with that of 
■ the Anthropoid Apes, we find the 
former distinguished by the fol- 
lowing three points (ef Figs, 60 
and 62) : — 

(1) Stronger development of 
the gi-eat toe.^ 

(2) Greater development of 
the tarsal elements. 

(3) Displacement of the great 
toe into a position of parallelism ^ 
with the other toes. ^ 

If the foot of a second 
month's human foetus be ex- 
amined, with special regard to 
the last point, it will be seen (Fig. 63, B) that the position of 
the great toe almost entirely agrees with that of the thumb 
(63, A). When the limbs are laid against the trunk, both point 
towards the head in the position of abduction. 

Whereas this is the normal lifelong position of the great toe 
of the Apes, and of the human thumb (cf. Figs. 60 and 61) in 
the human foot it is merely transitional, and is abandoned 

* We have lierein a noteworthy contrast to most of those lower ilammala in 
which the great toe ia reduced, or has altogether disappeared. A claw nwj in the 
fonner case be found at its distal end {e.g. in the Dog), but even that may diaagipear. 




10. — Skeleton of 
t Chiupanzee, Dorsal Aspect. 
tO'Cuneiform ; fn., ento-cuneiform; 
meso-ciineiforni ; cb., cuboid ; nv., 
navictilar ; aa., astragalus ; cl., cal- 
; I-V, digits. 



THE STRUCTURE OF MAN 



as early aa the eighth week of fcetal life. The definitive 
position (Fig 62) is, however, very gradually reached; for it is 
a well-known fact that the mobility of the great toe is far more 
marked in children at birth and in the earliest years of life than 
in adult Europeans.' In certain races (e.g. the Japanese) 




Fia. 61. — Skblbton 

ef., cuneifarm ; Iv,., lunar ; m 

trapezimii ; tps,, Ir. 



i Left Hand, Dohbal i 

; pc-, pisiform ; sc, ecaphoid ; 
, nneiform. I-V, digits. 



a considerable mobility ia often retained throughout life ; and 
the uses to which the great toe can be put fill a European with 
astonishment. 

Balz, in his work on The Bodily OharacterisHcs of the 
Japanese, says : " The use made by the Japanese of the great 
toe as a kind of thumb is very remarkable ; it can be independ- 

' The foot of a child which has not yet leamt to stand or walk is a particularly 
intel^sting study. Not only are the toos capable of performing complex movements 
(the great toe being even utilisable for grasping purposes), but the sole or plantar 
surface of the foot, in its form and in certain of its furrows, reflembles the palm of 
the hand far more than later, when socks and shoes have exercised an inSuence 
npon it. 



THE SKELETON 87 

©ntly moved, and so strongly pressed against the second toe that 
even small objects can be firmly held between them, A woman, 
when sewing, may hold the stuff with her toes, stretching it as 
she pleases ; and it is asserted that Japanese women can pinch 
effectively with their toes. In general, the foot of the Japanese 
has retained much of its natural mobility. These people seem 




FlO. 62.— SKBtKTOB 



(ib. + in,), utragalua (re^ideil as a product of fusion of the tibials and Intermedium of 
the tower vertebrata) ; cb,, ouboid ;cZ. (/b.). caliianeuiu (fibulare) ; ec., ecto-cuneiforia ; 
en., endo-cuDeiform ; mj., meao-cunBiform ; tir. (C), naricular (centrale) ; I-V, digits ; 
1-5, tarsalia. 



to be able to hold on to the ground with the sole of the foot ; 
and therefore when they need to stand firmly, as in fighting and 
wrestling, they are always barefooted. The first time one sees 
a Japanese man walking about with ease on a steep hoitse-top as 
if on level ground, it makes one feel quite uncomfortable, but 



88 THE STErCTT^i: CW MaF 

no fear of his falling need be CBt«fiilaJmBfl.. im hs> ^ojce aBcnrsseh- 
adapts itself to the surface of the TfHif ! '' 

[Although the great toe ctf iM^ adifli Innufiii «nl^ieci jntj tie 
thus thumb-like in function^ am ingr»anBiit ciiflffPffnt^ inffr^^eem 
the hallux and pollex e.xkt&. nm ifc ineanscamrr in ^^ilecHm 
to the former of an opponens HBuwdk. -Haeii a^ iF psesffiair m liie 
manus, and more geneiallr im fi»mii imicmxh ann i^ ni liie 
anthropoid Apes. The act irf ;giiasgnni! Irr :Ehe immiaii iaJhcs: 
differs from that by the pi^Iks nm fitHmg mte rd anfiie Ancrnmoa 
and closer apposition of the fiistt <fiiii£ ^s^umil riurtR? 

The cousins Sarasin haxe jwjciiiafifi om. libai hl :^ Xftooii"* 
foot the great toe stands ajpaort Sri^nn u^ itnhe; iiw&. saL isuc i^ 
last four metatarsals are toxiBi^ mwairSs^ liil^ irm mxt mrme '^iul 
in a European foot. Thi- w^ii^fie iimz iif likr duiXEei Jii^ sol 34e 
observed in the living staitife. [Em Bailnu: ^wrii 'xinf i»imn«!!Hwiit 
allowance must be probablr msmfi^ ibi: :^ xat ic A^ inwiir J^ nnure- 
important distinction^ finocL tih^ aumwitcii?^ Hnta^anuail ^umc «i£ 
view, is that the tarsos is miu^mflx ^ifi3!]^ mvL:nisnTcms: thoil a&afi 
of the European. If 10# be isiiiflL j&iitt lenpfi. a: :tm ««uni£ 
metatarsal in a Earopeaji, n&iHt I<i»l ^wmiic 3;gi??e»eiri :att lmgc& 
of the tarsus ; in the Yeii&A. iii ifr I: Jii jr iht frorilk 114^1. ayoif 
in the Chimpanzee 11^, so ti&uc t^ iitnsmr 3^ :taimi: 'ju msmms^ 
in length as we dieseend in tiiA ^ascs!^^ Jk ^am^sc nmunrcam. iiL 
breadth is also recf^jniaabfc. 

Acconling to Flitzner, w&u« ji:smmm i«*eraaams« jil n&fr 
variations in the human pei&I s&HiimjQ. Jtn (i: -^^lesSfcL mcmnsn nht^ 
variations in the proportions i}l tdiu itir*, u-jt ji. :t» lisi^l^ii. 'jf tfet 
rnetatarMak and phaJangtfSv ais iiir ^mio^ rtnui. :iiuaK it i;hi» 
hanri Thw applies espeeiafly Wi iJw ^piseir :ini iwnt ii» 
rwitatarml ; an<i correlatively. tin ti!iti>-<umi^(urm. :«- omsch. iniii!^ 
liahlft no variation than are txhe m««i- vimt a(Bi)st>^«:iHiii^<lurm. Thfr 
jw>-fialk<l Lwlirain^'s line i& alfio liable :?m ^"cirt^onwi. m. ife Q^un%;. 
and th'iik f^jipeciallT applies txj die liiirtt :iinHij^<i»^N»Mlhi^ 
rmn. The latter does noc a* a mitt ofj-mtuw^i :fc»t Hmk it: i^hif 
forirth narMo-metanarsaL artdcuianuu. 'Jiar *4wi»ft>a«i.cj«^ \^h ijx, 
r.onxerjui^nt apon die mode ii Jksxt^Ht^m. yi mttmk ^kiffit aKtati- 
r-vinf-iform ami the trjurdi meraau:«4i. .vm^ I4^ pM^li^l^ l^Hik-- 
wPiXiU Here, as well as in die :ii*U!«Sv '-^Wi Wt>: ti^ ^,1^. Mtttatt 
m-^.nt variation Ptitzner . The ^n??a- :m*. :;»> ii^ iittitt. i^t- auljr 
•ribHointAy hut reiunively lomstir ibmk Jk ^^ttW*^ ^^wL ttusb ifi: 
true of the thimib .ilso. — ^ 4iichc .-t^^isvttiiit^tilli^ -^i" th*^ \^ftd4^1itjMVwa: 
Haying that women repre^«ur :tiv :rAafj^irv«iMVt> .4tt^ i«9dit. d» 



THE SKELETON 



89 




1 



progressive element in human development — in other words, 
the greater development of the thumb and the great toe of the 
male must be considered as a recent acquirement. Accom- 
panying this difference in the first toe, we note also the 
slighter reduction of the length of the other toes, and especially 
of the middle phalanges, in Man, as compared with woman. Man 
has, as a rule, the original elongated type of toe ^ 

— ^woman the shortened and compressed type. 

Further interesting results might be 
obtained by a careful comparison of the tarso- 
metatarsal joint of the first toe in the various 
human races and in the Apes. 

While, thus, progressive development takes 
place on the inner or tibial side of the foot 
as the result of functional adaptation, the 
following retrogressive processes take place 
on the outer or fibular side : — 

The little toe is not infrequently two- 
jointed, the middle and terminal phalanges 
being synostotically confluent. Pfitzner found 
this to be the case in thirteen out of forty- . . , /T' " v v ^ 

•^ A, right fore - limb ; B, 

seven examples. This fusion, which is, as a right hind -limb, of a 
rule, found on both feet, is not due to the 
pressure of shoes or to any other mechanical 
causes,^ but to the fact that the little toe 
and its metatarsus ^ are in process of degene- 
ration. This process of reduction, which 
may end in the little toe becoming in a measure like the thumb 
and great toe, two-jointed, is particularly interesting, as it is 
taking place, so to speak, under our eyes. All stages from 
incomplete to complete fusion can be observed. Further, this 
degeneration of the little toe apparent in these facts can also 
be gathered from the condition of its muscles; [of these the 
flexor brevis often sends either but a very weak offshoot to the 
little toe, or, like the extensor brevis, none at all.] 




Fig. 63. 



human embryo in the 
second month of intra- 
uterine life, to show 
the similarity in posi- 
tion and direction of the 
thumb and the great toe 

(I). 



^ I find this synostosis also present in the skeletons of Egyptian mummies of 
various ages, not excluding children. It may here be remarked that, according to 
Balz, among the Japanese, who do not wear shoes, the little toe appears quite as 
reduced as in the European foot. 

^ We are at present unable to deal with the question of the significance of the 
independent origin of the fifth metatarsal tuberosity, which is the more surprising 
in consideration of the frequency of retrogressive processes on the fibular side of 
the foot. 



90 THE STRUCTURE OF MAN 

It Bhould, in paasing, be noted that the mutual rektionshipa between the 
muscles and bones are not abaolutelj similar in every single case, although a 
general agreement eiists. The undeniably close connection between the 
modifications of two must not be regarded as that of cause and effect, but 
rather as the joint effect of a common cause. 

also to be found in the other 
while the terminal and 



Clear signs of d^eneration 
toes, and especially their middle 




Fio. 61,— ^PosTKRiOH End of thb Body of two Human Embhtos, with thk 

Left HiND-LiitB and Umbilical Cord. 
t the end of tlie seventh week ; B, in the middle of the eighth week. The pOBitioD 
iwortby. cu., nnibilical cord ; cc., coccygeal ei ' 



ifthegreBttoe(I)isni 



basal phalanges may be also affected. The second toe is mostly free 
from signs of degeneration: its middle phalanx shows a disposition 
to shorten, but it at the same time tends to become stronger 
rather than weaker. It might, therefore, be predicted of the 
human foot that it may end by possessing only two two-jointed 
toes, the great toe and its neighbour ; ' but the possibility of 



' [It may be questioned whether it would not be nn 
there is anything in this argument at all, that all the 
second nay ultimately become two-jointed.] 



e correct to predict, provided 
let with the excepttOQ of the 



THE SKELETON 91 

development in other directions such as might counteract the 
present tendency must, however, be allowed for (Pfitzner).^ 

Comparison of the Fore- and Hind-Limbs of Man 

In comparing the opposite extremities of the adult two 
difl&culties have to be met, the first being that the knee and elbow- 
joint bend in exactly opposite directions, and the second that, 
owing to the inward rotation of the fore-limb, the homologous 
bones of the fore-arm and fore-leg (radius and tibia, ulna and 
fibula) are differently disposed. 

Martins and Gegenbaur have endeavoured to explain these 
difl&culties by spiral rotation of the humerus during development 
— said to be effected by alteration in growth of the epiphysial 
cartilage, with the addition of bony tissue at some points and its 
resorption at others. The distal end of this bone has its 
original ventral surface turned dorsally and vice versd. By 
comparing the position of the humerus in embryos and adults it 
is found to rotate through an angle of about 35° (Gegenbaur). 

Spiral rotation of the humerus actually takes place, not only 
in Man, but very commonly in other Vertebrates. It can further 
be proved that it progressively increases as we pass from 
the lower to the Caucasian races ; and Broca afiSrms that an 
increase is to be found at different epochs within the same race. 

But although the torsio humeri is an undoubted ontogenetic 
fact, according to more recent authors, it is questionable whether 
it affords any explanation of the difference between the fore- and 
hind-limbs. This subject is so important that we must enter 
into it at some length, referring especially to the works of Hatschek 
and HoU. The first of these investigators has rightly taken for 
comparison the lowest terrestrial Vertebrata, the tailed Amphibia, 
and he lays emphasis, upon the fact that in these animals the 
position of the fore- and hind-limbs in relation to the trunk is 
almost identical. Both stand out at right angles to the long axis 

* [It appears to me that the occasional longitudinal subdivision of the human 
hallux-tarsal (ento-cuneiform) into two distinct bones may be not improbably a 
phenomenon akin to that of the double ossification of the supra -occipital under 
expansion (cf. ante, p. 60), if not an actual index of jirogressive development 
now at work. My friend Professor Arthur Thomson informs me that, from a study 
of the articular surfaces of this bone, he believes the tendency towards duplication 
to be more general than is customarily assumed ; and it would be most interesting 
to inquire whether among the Seals and Walnises, in which the inner and outer 
digits are one or both similarly dominant over the rest, indications of a correspond- 
ing variation might not be forthcoming in the foetal state. — G. B. H.] 



92 



THE STRUCTURE OF MAN 



of the body. The elbow and knee joints are turned slightly 
outwards, the convexity of the former facing slightly backwards, 
that of the latter slightly forwards. The supporting portion of 
the limb looks in both cases outwards, and in each the anterior 
digit is rightly considered as the first of the series. 




B 




Fig. 65. — Larval Salamander. (After Hatschek.) 
A, with the limbs turned down ; B, with the limbs turned up. 

In the higher Quadrupeds the anterior and posterior limbs 
imdergo characteristic changes of position. First, the supporting 
segments of the two limbs (i.e. the manus and pes) are rotated 
inwards, so that their long axes, which were originally transverse 
to that of the body, come to be parallel with it [and their 
originally anterior borders become internal] ; as a natural result of 
this, the first digit (poUex or hallux) becomes the innermost and 
the fifth the outermost. The rest of the limb, however, differs in 
its behaviour in the two members. In the fore-limb the humeral 
and radio-ulnar segments become flexed in such a way that the 
elbow is no longer directed outwards but ba,ckwards (cf. Fig. 65). 
In the hind -limb, on the contrary, the basal (femoral and 
tibio-fibular) segments are turned inwards, and so flexed that 
the knee is directed forwards. According to Hatschek the 
differences in position of the fore- and hind-limbs involve only 
their basal segments, their terminal segments (manus and pes) 
being displaced identically. It would follow from this that the 
changed position of the fore-limb has little if anything to do with 
the torsion of the humerus, which is very marked even in the 
Salamander, and must therefore be referred back to an early 
process antecedent to the changes under discussion. 




THE SKELETON 93 

Holl also repudiates the torsio humeri as the most important 
factor in effecting the torsion of the fore -limb. He, unlike 
others, considers that there is no very great difference hetweeu 
the position of the bones of the 
forearm and the fore-leg in Man. 
He rightly points out that the 
tibia and fibula do not lie parallel, 
but that the fibula lies external to 
and behind the tibia, and insists 
that it thus occupies, in relation 
to the tibia, a position similar to 
that of the ulna in relation to the 
radius.' In instituting these com- 
parisons we ought to start with 
the hind-limb, which is simply 
BO rotated at its base that the 
whole of its raorphologieaUy ven- 
tral surface becomes posterior in 
position, and not with the fore- ^"^ e6.-SKELEK.!. of a Yoog Beah 

f. , ' , » , - , - , ILLUSTRATISG THE POSITIOSS OF TBB 

limb, the torsion ot which mvolves Limbs. (Aiwr Hatschefc.) 
the independent segments individ- '■^- ^'^ '^^,^'.^''11,^' "*"" ' 
ually, and should therefore be 

excluded in endeavouring to settle the question of homology. 
This consideration excepted, Holl agrees in the main with 
Hatschek as to the Quadrupeds ; but he extends hia observations 
to Man, and declares that if he be regarded as a Quadruped, the 
changes of position in the limbs are such that the homologising 
of them with those of Quadrupeds is not difficult, i.e. if a man 
goes on all fours the position of the shoulder girdle and with it 
that of the humerus is slightly altered. The head of the latter 
no longer points forwards, but backwards, and its great tuberosity 
comes to point forwards, just as in the quadrupedal Mammals, 
the distinction formerly established between them and Man in 
this particular thus disappearing. 

' [Hail a)ipears to have ineaffioientlv appreciated the primary dispositioD of the 
limb-buds. The postero- internal displacement of the fibula upon irhich he lays such 
■tiRB 13 Kell marked in the Mar^iipiaU. vhich, with the eiception of the Dasrnridr, 
bsTe an opposable hallut;. DeUtled eiamination of the boned of the fore-leg of 
mne of these aninials and of the muscles which control theit rolatorr (so-caJled 
" pronator ''i morements, prores iLat the adaptive modification which the hind-limb 
has at «nj rate here undergone is of a distinct order from tbal of the fore-limh above 
desmbed (cf. Young, Jmir. Anal, and Phta., voL ir. p. 392). And it mar be 
ineidentallr remarked that an opposable hallux appears independenllv atnOBg 
3e common Dormouse.] 



.• •< 



94 THE STRUCTURE OF MAN 

For the further study of the processes by which the limbs 
are displaced during development, I must refer the reader to the 
works of von KoUiker, HoU, and others. It should, however, be 
remarked once more that the twisting of the hind-limb occurs 
at the hip-joint merely, [and affects the limb as a whole, its 
originally ventral surface becoming posterior and its dorsal 
anterior in position, and that in the fore-limb the twisting most 
conspicuously affects the manus and the forearm, the radius under- 
going a marked inward rotation upon the ulna. The humeral 
segment more nearly retains in the adult its original position], and 
the rotation and retroflexion which it ultimately exhibits chiefly 
result from a twisting of the shoulder girdle, with accompanying 
modifications of its articular head. 

These changes in position of the shoulder girdle are connected 
with the development of the thorax. As long as the latter retains 
the laterally compressed form characteristic of most Mammals, 
and is not expanded dorsally, the scapula lies at its side. Later, 
when transverse enlargement and consequent dorsal expansion of 
the thorax are effected (cf antCj p. 36), the scapula comes to lie 
upon {i.e. dorsad of) it. This change in the thorax plays a leading 
part in altering the position of the shoulder girdle as a whole, 
and of the limb attached to it. 

If we wish to homologise the two pairs of limbs scientifically, 
we can only do so by tracing their displacements back towards 
their embryonic positions. 

Changes of Position of the Limbs in relation 

TO THE Trunk 

A comparison of the fore-limb of Man with that of the lower 
Vertebrates, and especially of the Fishes and Amphibians, and a 
careful analysis of the courses and relationships of its muscles and 
nerves with respect to the trunk and the spinal cord, lead ug to 
the conclusion that the shoulder girdle and its associated limb 
originally lay farther forwards, i.e. nearer the head. The dis- 
placement backwards most probably took place, as has already 
been shown {ante, p. 44), simultaneously with the disappearance of 
the cervical ribs — indeed the loss of the latter certainly helped 
to bring this about, by compelling the scapula and clavicle to 
find points of attachment farther back on the thorax. 

. Whereas this shifting of the fore-limb takes place from before 
:backwards, that undergone by the hind -limb is from behind 



THE SKELETON 95 

forwards, i.e, towards the head. Both these alterations in position 
are most clearly reflected in the variations of the nerve plexuses 
of the limbs, the origin of which will be discussed later. We 
must, however, first ascertain what these variations are. 

The lumbo- sacral plexus, as compared with the brachial, 
is the more subject to variation, and the less definitive. Even 
if the brachial plexus does show slight inconstancy, no such 
marked differences in the origin of its component nerve trimks 
occur as in the lumbo -sacral. In most cases, these varia- 
tions in the limb plexuses are accompanied by variations in the 
vertebral column. For example, when the lumbo-sacral plexus has 
a markedly caudal origin, a supernumerary presacral vertebra 
usually occurs ; here we have an atavism, i.e. an indication of the 
primitive arrangement under which, as above described (ante, 
p. 33), the pelvis lay farther back. But we know that, during 
ontogeny, the pelvis undergoes a forward translocation. Cor- 
relatively, the lumbar plexus assimilates nerves lying farther 
forward than those which primarily formed it (the ileo-hypo- 
gastric, ileo-inguinal, and the genito-crural), while the posterior 
sacral nerves of the adult show signs of instability and degenera- 
tion, and may gradually altogether disappear. 

The forward gathering of the nerves for the hind-limb is 
naturally accompanied by modification in the innervation of 
those parts of the urino-genital and alimentary systems which 
lie in the pelvis. These are obviously dependent on the pelvic 
girdle, and compelled to follow when it shifts along the verte- 
bral column. The ischiadic and the pudendal plexuses are so 
closely connected that they could not in any case be separated ; 
but the relationship between the pudendal and caudal plexuses is 
less intimate, and if the former shifts forwards with the crural 
plexus, its distal elements separate from it. These retrogressive 
nerves of the caudal region would necessarily increase in number 
in proportion to the forward translocation of the hind-limb, if 
the caudal region itself did not at the same time shorten 
(Eisler). 

We thus have transition zones ; and this becomes the more 
clear the farther the lumbo-sacral plexus shifts in a proximal 
direction. In extreme cases variation may extend as far 
forwards as the eleventh thoracic nerve, which then sends a 
loop to the twelfth. 

Similar phenomena accompany the backward displacement of 
the fore-limb, but this, as already mentioned, appears to have 



96 THE STRUCTURE OF MAN 

nearly attained its definitive position.^ The brachial transition 
zone is consequently more restricted and stable than the lumbo- 
sacral, rarely extending backwards beyond the second thoracic 
nerve. If, however, the upper limb preserves its original position 
(the seventh cervical rib persisting), the brachial plexus receives 
either no contribution or at best an insignificant one from the 
first thoracic nerve (Eisler). 

Even if this conception of the " metameric transformation 
of nerves," deduced by Furbringer, affords a partial explanation 
of the existence and present condition of the nerve plexuses, the 
actual causa movens lies deeper, i,e. in the original polymeric 
origin of the limbs. In the region from which they develop we 
meet with traces of a gradual fusion of originally distinct segments 
(somites), with further clear traces of the shifting which they 
have imdergone during phylogeny. An excellent illustration of 
the commencement of fusion among the body segments is yielded 
by the transitional zones just defined. Quite apart from the 
already-mentioned variations of the nerves, the primitive segmenta- 
tion of the ventro-lateral body muscles is gradually being obliter- 
ated, and the myocommata with the ribs are becoming vestigial — 
in fact the whole ventral body-wall is affected by this process 
of fusion (Eisler). 

^ That a further shifting of the human fore-limb in an antero-posterior direction 
may be expected is evident, firstly, from the varying relation of the brachial plexus to 
the anterior thoracic nerves ; and, secondly, from the very rare, yet occasional, retro- 
gressive condition of the first thoracic rib before mentioned {antCf p. 43). 



MUSCULAE SYSTEM 

As might be expected, we find, in the 200 to 250 muscles 
which form the active motor apparatus of the human body, 
variations far greater and more numerous than any already 
described in the different parts of the skeleton. 

It may confidently be asserted that hardly a single human 
subject has been examined which has not shown some variation 
or other in the muscular system ; and in a great number of 
bodies new muscles are discovered which have not before been 
observed, and of which no mention can be found in text-books. 

Considering this " embarras de richesse," we may be excused 
for entering in the following pages somewhat into detail ; it is, in 
fact, absolutely necessary to do so in order to get a general idea 
of the immense mass of material available. Of the extent of this 
variation an approximate idea may be obtained from the fact 
that my French colleague Testut, in his work of 900 pages on 
the muscular anomalies in Man, has by no means exhausted the 
subject. 

Examples will be considered in the following order : — 

(1) Eetrogressive or vestigial muscles. 

(2) Muscles which, appearing only occasionally, are considered 

to be atavistic. 

(3) Progressive muscles. 

This order cannot be rigidly adhered to, inasmuch as both 
progressive and retrogressive development have been observed to 
take place, side by side, in one and the same muscular region. 
It is further to be noted that those muscles which are actually 
progressive as far as the genus Homo is concerned, are not recog- 
nisable as such in mere individuals ; their anomalous conditions 
can only be considered as individual variations until traced 
through successive generations, i.e. imtil it is proved that they 
are inherited. 

An accurate knowledge of Comparative Anatomy and Ontogeny 

H 



98 THE STRUCTURE OF MAN 

is necessary, to facilitate judgment and sharpen observation, in 
dealing with both progressive and retrogressive variations, which 
latter are the preliminary stages in degeneration. In the critical 
examination of the muscles, as pointed out by Fiirbringer and 
Euge, it is primarily important to ascertain their innervation. 
The nerve-supply is the safest criterion as to the morphological 
value of a muscle. 



RETROGRESSIVE MUSCLES 

Of the Trunk 

The dorsal upper and lower serratus are, as is well known, 
connected together by a strong silvery aponeurosis. This is 
occasionally replaced by muscular tissue, which, in connection 
with the upper serratus — less frequently with the lower — 
may extend down as far as the sixth rib. This clearly points 
back to a primitive condition in which the two muscles were 
continuous. In contrast to this variation there occur others in 
which the two serrati are much less developed than usual, so much 
so that one or both of them may be entirely wanting. This is 
very important, as it leads to the conclusion that the serrati, like 
many other muscles, are being gradually transformed into tendinous 
tissue. The cause of this must be sought in the modification of 
the respiratory mechanism of the thorax, and the samp would 
appear to be the rationale of the many variations of these same 
muscles observed in the Anthropoids (cf. ante, p. 45). 

The degeneration of the caudal region in the human body 
has naturally been accompanied by a corresponding reduction of 
the related muscles, i.e, especially of those the homologues of 
which, in caudate Mammals, are strongly developed for moving 
the tail. These are serial with the musculature of the trimk, 
and can be divided into a ventral and a dorsal group. To the 
latter belong the extensor and levator coccygis, which lie along 
the posterior surface of the coccygeal vertebrae. This extra- 
ordinarily thin muscle bundle arises either from the great sacro- 
sciatic ligament or from the lowest end of the sacrum, and sends 
out tendinous rays towards the apex of the coccyx. 

To the ventral series belongs the coccygeus muscle, which 
arises from the spine of the ischiimi, rims along the lesser sacro- 
sciatic ligament, and is inserted into the lateral edge of the coccyx. 
This muscle brings about the lateral movement (abduction) of 



MUSCULAR SYSTEM 99 

the tail in the lower Mammals, and is therefore termed in them 
the abductor eaudalis. 

The curvator coccygis, which is met with on the anterior 
surface of the lower sacral and sometimes of the upper caudal 
vertebrae, belongs to this same category. It corresponds with 
the depressor caudse of the lower Mammals. 

The vestigial character of all these muscles is in several ways 
evident. They vary in form and size, and may be partly or 
wholly replaced by fibrous tissue, or, finally, one or other of 
them may be altogether wanting. This is also the case in the 
Anthropoids, where (e.g. in the Orang) their vestigial character is 
in some ways more pronoimced than in Man. 

Another caudal muscle may here be referred to, although 
morphologically it does not belong to the above-mentioned series. 
This is the caudo-femoralis (agitator caudse) which, in a large 
number of Mammals (Monotremata, Marsupialia, most Carnivora, 
Lemuroidea, and tailed Monkeys) plays a great part, as flexor 
and abductor of the tail when the thigh is fixed, and which, in 
exceptional cases, appears in Man also. It lies at the lower edge 
of the gluteus maximus, being separated from it by only a small 
space. It arises from the lateral edge of the coccyx or of the last 
sacral vertebra, and is inserted into the femur below the point of 
attachment of the lowest bundle of the gluteus. 

Normally, this muscle is wanting in Anthropoids, but it is 
not improbable that it may occasionally reappear in them as in 
Man. 

In both the dorsal and ventral trunk muscles we find indica- 
tions of original segmentation. In the intercostal muscles the 
segmentation is completely retained, and not infrequently tendons 
pass from the ends of the lower ribs into the broad abdominal 
muscles. Cartilaginous tracts are sometimes found persisting in 
a line with these tendons, but nearer the median plane, and 
they may be either free or connected with the tendons. Even 
in cases where all such indications are wanting, the innervation 
of these muscles points to a primitive metamerism. 

In the same way, the rectus abdominis, by its "inscrip- 
tiones tendineae," shows a more or less distinct segmentation. 

This muscle in the lower Vertebrates {e.g. tailed Amphibians) 
extends from the pelvis to the head region ; but in the higher 
Vertebrates, and particularly in Mammals, in accordance with 
advancing modification, and especially with the intervention of 
the sternal apparatus, it has become divided into a posterior and 



100 THE STRUCTURE OF MAN 

an anterior tract. The former arises from the pelvis, and is 
inserted anteriorly, as a rule, on a level with the fifth rib ; the 
latter is represented by the ventral cervical muscles, viz. the 
sterno-hyoid and sterno- thyroid, which here and there bear 
inscription's tendineae indicative of their former segmentation. 
To these must be added the almost constant omo-hyoid, which 
is provided with an inscriptio, and the thyro-hyoid. Farther 
forward these are joined by the hyo-glossus, genio-hyoid and 
genio-glossus, which belong to the same metameric series.^ 

In the lower Primates the rectus abdominis muscle still 
reaches to near the first rib, and thus recalls the connection 
with the cervical musculature mentioned above, which was first 
lost in the Eeptiles. Even in Man it may sometimes run beyond 
the fifth rib and, imder cover of the pectoralis major, pass as far 
up as the second. This is a striking case of atavism. 

In the higher Primates the thoracic head of this muscle 
shifts back to the lower ribs, and this shifting towards the 
abdominal region is accompanied by an advancing loss of 
segmentation in both the Anthropoids and Man.^ But even 
where this is most marked the muscle has not quite lost its 
thoracic character. 

This retreat of the rectus muscle is intimately connected 
with the development of the great adductor of the fore-limb (the 
pectoralis major), since it is only when the upper parts of the 
rectus disappear that the muscular bimdle forming the pectoralis 
major — and, indeed, that forming the pectoralis minor as well — 
is able to take possession of the firm anterior thoracic surface 
furnished by the ribs. Where, as in the lower Apes, the anterior 
end of the rectus muscle covers the thorax as far as the lateral 
edges of the sternum, a primitive condition being thus retained, 
those fasciculi of the pectoral muscles which arise from the 
skeleton come simply from the sternum. " We here have a con- 
flict at close quarters between different parts of the organism " 
(Euge).« 

In connection with his studies of the abdominal musculature, 

^ [Cf. Albrecht. Beitrag z. Morphologic des M. omo-hyoides u, d. vervtr, inneren 
InterhranchialmiLsculatur i. d. Reihe d. Wirhelthiere. — Inaug. Diss., Kiel., 1876.] 

2 In many cases the muscle withdraws in a distal direction even farther than 
the fifth rib, and derives its anterior (uppermost) slip from the sixth. A primitive 
slip from the eighth rib may also be retained (Ruge). 

3 Where, as a rare anomaly, the rectus abdominis is double on one or on both 
sides, a very low condition is indicated, this arrangement being typical in Amphibia 
and Saurian s. 



# « 



MUSCULAR SYSTEM 101 

Euge has called attention to a phylogenetic shifting of the navel. 
This occurs during the shortening of the thoraco-lumbar portion 
of the trunk (in relation to the segments of the rectus abdominis), 
and is accompanied by a gradual elimination of the posterior 
segments of the rectus. This process may not be yet finished ; 
if, as has already been argued in dealing with the vertebral column 
(antey p. 43), a progressive abbreviation of the thoracic region of 
the trunk is still taking place. 

In front (ventrad) of the point of origin of the rectus 
abdominis, at the upper edge of the pelvis, there lies, in Man, 
the inconstant pyramidalis abdominis muscle. This is sometimes 
developed only on one side, and sometimes unrepresented, in 
which case it may be replaced by a tract of fibrous tissue. On 
the other hand, either one or both halves of this muscle may be 
double ; and there are variations no less remarkable in its form 
and size. The pyramidalis usually runs either about half-way from 
the symphysis pubis to the navel, or only a third of that distance ; 
it may sometimes, however, reach as far as the navel. In young 
children it is relatively larger than in adults. These facts may 
all be taken as evidence that the pyramidalis in Man (and the 
same applies to many Mammals, e,g, the Anthropoids) possesses 
all the peculiarities of an organ which has long been in a state 
of degeneration. It claims our attention principally as a striking 
example of the tenacity with which certain structures remain 
in the organism and are handed on, through inheritance, long 
after they have lost their specific significance. The reason for 
such continuance can only be that, in the course of phylo- 
genetic development, the muscle has imdergone a change of 
function, and has become associated with or subordinated to 
other muscles or groups of muscles. In this case the pyramidalis 
has been overmastered by the rectus abdominis. 

In the non-placental Mammals (Monotremata andMarsupialia) 
the pyramidalis is powerfully developed in connection with 
the epipubes (so-called marsupial bones) ; and even in some 
Placentalia, such as the Insectivora {e.g. Myogale fyrenaica), it may 
almost reach the ensiform process of the sternum, thus playing 
an important part in strengthening the abdominal wall. The 
pyramidalis is undoubtedly an old muscle dating far back to 
pre-Mammalian times. 

Both the abdominal oblique muscles may be considered as 
continuations of the intercostal muscles into the abdominal region, 
and, anteriorly, the scaleni muscles of the neck may be looked 



102 THE STRUCTURE OF MAN 

upon as forward extensions of the same. The neck, as has been 
seen from the study of the skeletal system {ante, p. 43), was 
formerly provided with free ribs ; and hence this serial relation- 
ship of the cervical to the segmental thoracic mu3cles is easily 
understood. The degeneration of the cervical ribs has had 
(among other results) the effect of causing the short-fibred scaleni 
muscles, which once only stretched across the intercostal spaces, 
to unite and grow longer, so as finally to reach ribs which lie 
farther back. Further related modifications may be exemplified 
in the occurrence of supernumerary scaleni, such as the scalenus 
minimus (scalene intermediaire, Testut), which is typically present 
in all Anthropoids, and by the numerous variations in origin and 
attachment of the three ordinary scaleni. 

The transversus thoracis muscle (triangularis sterni) is clearly 
degenerating. This muscle, which lies on the inner side of the 
anterior wall of the thorax, arises from a variable number of slips. 
It arises, as a rule, from the cartilages of the third to the sixth 
ribs, and occasionally receives a slip from the seventh rib also. 
This fact helps us in homologising it as a continuation of the 
transversalis abdominis. These two muscles are separated by one 
of the bundles which give rise to the diaphragm. 

The Muscles of the Cervical and Cephalic Eegions 

In addition to the structural changes going on in the scaleni, 
which have been already mentioned, the following facts are worth 
recording : — 

The original community of the trapezius and the sterno- 
cleido-mastoid muscles is indicated by their common innervation, 
and further by the fact that the interval between them is still 
not infrequently occupied by the cleido-occipitalis which runs 
from the clavicle to the occipital bone. This muscle thus forms 
a link between the trapezius and the sterno-cleido- mastoid, 
and when strongly developed brings about a more or less 
complete fusion of these two muscles, i.e. reinstates the original 
condition. 

These facts might have been included in the remarks on 
muscles which occasionally appear and may be considered atavistic, 
but they are here dealt with as they indicate a gradual dis- 
appearance of certain fibrous areas in the region of these muscles, 
i.e. they point to a retrogressive condition. 

A similar relationship exists between the anterior belly of 



MUSCULAR SYSTEM 103 

the biventer maxillae (digastricus) and the mylohyoid (as may be 
gathered from their innervation), while the posterior belly of the 
former may sometimes fuse with the stylohyoid. 

Undoubtedly the most interesting of all the retrogressive 
muscles of the cervical region is the so-called platysma myoides 
(subcutaneus colli). This muscle is also related, as will be 
shown later, to certain cephalic muscles, and requires a more 
detailed description (cf infra, pp. 104 and 114). 

Whereas most muscles are closely connected with the skeleton, 
there are, in the Vertebrates, certain muscles which both arise 
from and are inserted into the integument or the subcutaneous 
tissues. These are the cutaneous muscles (panniculus carnosus 
of the lower Mammalia). 

These cutaneous muscles are [with rare exceptions] only 
feebly developed among Fishes and Amphibia, but in Eeptiles 
and Birds they play a great part in connection with the scutes, 
scales, and feathers. They are, however, most developed in 
Mammals, in which they may spread like a mantle over the back, 
head, neck, and flanks {e.g. IIchidna,Das2/pus, Pinnipedia, JErinaceus, 
and others). 

In Man and the Antliropoids only feeble traces of this 
musculature are found, such as the platysma-myoides already 
mentioned, which spreads over the upper part of the thorax and 
the neck and partly over the face (cf Fig. 67). Other slight 
traces are foimd in the shoulders, back, abdomen, axilla, forearm, 
hand, and buttocks. 

Among the lower Mammalia the panniculus carnosus fimctions 
as a protective against injury to the skin. The reaction of the 
skin of horses when stung by insects may be given as an example 
of this. 

The mimetic musculature is very closely connected with the 
cutaneous, and is at least partly to be derived from it phylo- 
genetically. In a general sense, the differentiation of the 
mimetic musculature may be said to advance with advancing 
intelligence ; and we may therefore expect to find it most highly 
developed in the Primates. 

The phylogenetic development of this system has been 
studied by Gregenbaur and Euge. According to Gregenbaur, the 
human platysma appears to be the remnant of a musculature 
which was continued on to the head, but which has only retained 
its primitive imdififerentiated condition on the neck. The chief 
reason of this is that the platysma, even in Man, is sometimes 



104 THE STRUCTURE OF MAN 

directly connected with the zygomatieua minor, the orbicularis 
palpebrarum, the auricularia anterior, and the transversus nuchfe. 
On the other hand, however, the fact that the mimetic musculature 
is innervated by the facialis (n.fc.. Fig, 69), a nerve which, by 
location and distribution, is connected with certain muscles of the 
visceral skeleton, compels us to conclude that this (the mimetic) 
musculature has to some extent wandered from its original 




FlO. 67.— DiAORiU OF THE DISTRIBUTION OP IBS PLATYBUA OVER THE HbAD. (After 

Gegentuar.) The larger areas ar« marked with Bomaii figures, the Gmaller with 
letters (cf. with Fig. 70). 

position. It would appear to have moved up from the region of 
the lower jaw,' and to have entered into close connection with the 
soft parts surrounding the auditory and buccal apertures, i.e. with 
the lips and with the pinna, which are themselves of secondary 

' According to KilUan, it ia more than doubtful whether Ruge is right in 
assuming a post-auricular upward wandering of tbe platysma. Eillian holds that 
the pars occipitalis of the platysma had from the beginning a dorsal position, and 
that it ia nothing more than the posterior superficial layer of the dorsal portion of 
the musculature of the hyoid arch, as it appears not only in most Mammalian 
groups, but also in many species of Birds, e.g. Owls, in which even estemal auditory 



MUSCULAR SYSTEM 105 

or^n. In time the eyes, forehead, temples, and the parietal 
region were reached. 

In the Lemnroidea the mimetic muscles, instead of heing 
sharply individualised as in Man, are not anatomically distinct, 
i.e. they are merely parts of a great muscular tract, in which a 
superficial and a deeper layer can be distinguished (cf. Figs. 68 




Fia. 68.— SuPBBnciAL Mdscclatubb op thb Facs in LepilemvT muadiam. 
(After Ruge.) Th« deeper layer {m aj^iiitUr colli) is risible in the Deck. 

and 69). The superficial layer is the platysma, the deeper the 
so-called sphincter colli. 

In those exceptional cases in Man, in which the cervical 
portion of the platysma is developed, it is called the transversus 
nuchie. Schultze found this in eighteen out of twenty-five 
bodies, Macalister in 35 per cent; others, however, have been 
less fortunate. It was always foimd to be symmetrical, i.e. 
developed on both sides. This muscle, which is almost always 
present in the himian embryo, cori'esponds in position with the 
protuberantia occipitalis: from this it radiates outwards along 
the linea semicircularie, towards the tendon of the sterno-cleido- 
muscles split off from it. It is also found in Reptiles (Saurians and Chelonin). In 
Crocodiles a vestige of it is found in the powerful levator auriculje. Even in 
AmpliibianB and Sharks this iniisoiilar tract is already developed, and from it can be 
derived those human muscles which are innervated by the ramus auricularis posterior 
nervi facialis. 



106 THE STRXJCTUEE OF MAN 

mastoid or e-ven aa far as the posterior edge of the aiuieiilari'5 
posticus It may e\eii completely fu&e with the latter which 
thus appears to arise from the protuberantia occipitalis as seems 
to be the case with many lower Mammals 

The second and deeper layer of this cemcil muscle the 



fup ' aurc oicipit 




—Facial Muscles akd Nerveh of the Lemwoid pmpithecua. (After Euge.) 
Superficiil muscles with the branchings of the facial nerve {^l/(^ ). 

sphincter colli, runs from the occipital region over the edge 
of the jaw to the regio parotideo-masseterica, the lip and 
adjacent parts. We shall consider later which of the human 
facial muscles are derived from this, and which from the 
platysma ; at present we need only deal with the vestiges, often 
very slight, of this musculature which was probably incom- 
parably more developed in the ancestors of Man. Those 
mimetic muscles which are found partly near the ear and partly 



MUSCULAR SYSTEM 107 

on the cranium, show great individual variation, those on the 
right sometimes differing from those on the left in one and the 
same person. By taking their physiological activities into 
account we can establish three or four stages in their 



These mtisclea may be dealt with in four series, as under : — 
1, Muscles of the cranium, known collectively as the 
epieranius. Of this the frontal portion (irontalis) is still under 




Fia. 70. — MoflCLES of the Epicranial Reoios in Mas 
Facial MnacLia. (Alter Gegenbaur.) 
ap., epicrsDial aponeurosis ; a.p., posterior auricular muscle ; al., attolUns auriculaiu ; 
/)-., frontalis muscle ; g.ji,, iiarotid gland ; ins., masseter ; oc., ni. ocoipitnlis, 

control of the will, as is seen in frowning ; but the power^of 
throwing the entire epieranius into contraction, as in moving the 
scalp, is possessed by but few individuals. 

2. Muscles round tlie pinna : attrahens, retrahens, and 
attollens aiu-iculam (cf. Figs. 70 and 71). The capacity for 
moving these muscles varies greatly in individuals. In most jKOple 
it is entirely wanting ; and the retrogressive character of these 
muscles is due to the degeneration of the pinna (cf, infra). 

3. Intrinsic muscles of the pinna (derivatives of the muscles 
mentioned under 2, which liave become exclusively related to the 



THE STRUCTURE OF MAN 



pinna, and there i^ain further differentiated). Among these 
may be mentioned certain bundles which separate off from the 




Fia. 71.— A, Pinna of a Pbimateidivid. 

THAT OF THE AUDITOHT BmINENCEB O 
later formed ACDITORT FoLD ; 4, ITS BaSB. 

B, pinua of Mftn, of a BabooD and of an Ox, drawn to the same scale and superposed, 
s'., spina or tip of the ear In Man ; s"., the same of the Baboon ; and a"'., the same 
of the Ox (homologous points) ; C, pinna of J/ootcus rhesus, with the tip (j.) 
pointing upwards ; D, pinna of Cereopilheciis, with the tip pointing liacliwaidB ; 
£, pinna of Man, with ita muacles ; m.a., attoUens anricnlam ; m.a'., antitr^cus ; 
m.t., tragions ; m.t'., inconstant muscle bundle, stretching from the tragicus to 
the edge of the helix ; m,i,',, helicis m^oF ; mJi'., helicis minor ; s,, tip of the ear 
(spina) rolled over ; A-D, after Schwalbe ; E, after Henle. 

retrahens auriculam, chief of which are the transversus and 
obliquus auriculam (auricularis proprius, Euge) which, belonging 
to the most folded part of the pinna, are very small. 



MUSCULAR SYSTEM 109 

The helicis major (Fig. 71, m.h\) and the tragicus {m.t.) 
(the second of which is often wanting), are to be derived from 
the scutulo-auriculare (a portion of the depressor helicis, Euge), 
found in those Mammals which still possess a free and movable 
scutulnm. The helicis minor (m.^".), antitragicus (m.a\), and the 
incisurae Santorini, which belong to the cartilaginous wall of the 
external auditory meatus, are the proper ear muscles (auriculares 
proprii), and related to the principal cartilages and the pinna 
alone. 

Taking all the facts into consideration, this intrinsic muscu- 
lature of the pinna, which is no longer under the control of the 
will, must be considered as the vestige of a primitive apparatus 
fimctional either for the opening and closing, or for the widening 
and narrowing of the auditory funnel and the external auditory 
passage (cf. chapter on the auditory organ, infra). 

4. To the fourth class belong those mimetic muscles which 
have undergone the greatest degeneration, i.e. those which have 
become transformed into tendinous or membranous structures 
(fasciae). For example, the auriculo- (temporo-) labialis muscle of 
the Lemuroids (cf. Figs. 68 and 69) has, in Man, been replaced 
by the fascia temporalis superficialis, and the sphincter colli 
muscle by the fascia parotideo-masseterica. A great part of the 
human epicranial aponeurosis (galea aponeurotica), further, 
consists of muscle bundles of the occijritalis transformed into 
tendons. 

[It is interesting to note that the power of contracting the platysma, the 
ear muscles, and others not normally under the control of the will, has been 
observed in a few cases to go hand in hand with that of a voluntary con- 
trol of the heart's action.] ^ 

Muscles of the Limbs 

The palmaris ( = p. longus) and its homologue in the hind- 
limb, the plantaris, are time honoured (and certainly among the 
best) examples of the gradual degeneration of a muscle. The 
degeneration of the former has not yet proceeded as far as that of 
the latter, as is most evident in the fact that while the palmaris 
still reaches the palmar fascia of the hand, the plantaris only in 
exceptional cases becomes connected with the homologous plantar 
fascia of the foot, and in doing so regains its former significance 
as a flexor of that organ. 

The plantaris must therefore, as an original flexor, have 

^ [Cf. E. A. Pease, Boston Med. and Surg. Jour., 30th May 1889.] 



no THE STRUCTURE OF MAN 

begun to degenerate from the time that the plantar fascia became 
secondarily attached to the calcanenm, and helped in the forma- 
tion of the arch of the foot, as the latter became transformed 
into a supporting organ. 

But why are the palmaris and plantaris of Anthropoids, 
in which such transformations do not take place, also in a 
degenerate condition ? It does not appear difl&cult to answer 
this question if we consider that these muscles originally 
extended, as do their homologues in the lower Mammals,^ 
through the mediation of the palmar or plantar fascia to the 
phalanges, and acted as common flexors of the fingers and toes. 
If so, in the course of time — to confine our attention to the 
hand — as the flexores digitorum communis superficialis and pro- 
fundus became more extensively and more subtly differentiated 
from the primitive " pronato-flexor mass " (Humphry), the fibrous 
terminal expansions of the palmaris withdrew more and more 
from the fingers, and found points of attachment in the palm of 
the hand and in the ligamentum carpi transversum. Thus 
would the finger flexor appear to have become a hand flexor. 
As such, however, it could not, on account of its attachments, 
develop the same strength as the proper hand flexors,^ which are 
directly attached to the skeleton, and which, as we see where 
the palmaris is wanting, are competent alone to bend the hand. 
The palmaris becoming thus superfluous, is variable and occasion- 
ally absent. 

A further consequence of the transformation of the hind-limb 
into a supporting and ambulatory organ, is that some of the 
flexor muscles which originally ran down without interruption to 
the sole of the foot have become interrupted at the protuberantia 
calcanei by the dorsal flexion entailed. Another muscle of this 
flexor series, e.g. the short flexor, which corresponds with the 
flexor digitorum communis superficialis of the hand, has shifted 
its point of origin farther and farther down, till at last, on the 
acquisition of the upright gait, it has reached the calcaneal 
tuberosity. In doing so this muscle has become more and more 
closely connected with the plantar fascia ; and at present it 
shows in many ways, e.g. in the variation of its terminal tendons 

^ It is said that in Negroes tlje palmaris is still not infrequently inserted into 
the metacarpals. 

- That it is still functional in the hand is shown by its occurrence, which must 
still be considered normal. It is absent on one or both sides in about one in every 
ten bodies. 



MUSCULAR SYSTEM 



and the frequent absence of that to the fifth toe, evidences of a 
retrogressive tendency. 

The special extensors of the fingers undergo similar variations, 
being now as a rule restricted to 
the thumb, the index, and the 
little fingers. Occasionally, how- 
ever, the third and fourth fingers 
also receive tendons from the ex- 
tensor minimi digiti,andthe middle 
finger may receive a tendon from 
the extensor indicia propriua. 

The changes brought about in 
the sole of the foot naturally affect 
the dorsum as well There can 
indeed be no doubt that changes 
have taken place in the extensor 
brevis digitorum of the foot (e.br., 
Fig. 72) complementary to those 
above described in the flexor digi- 
torum communis brevis. The 
extensor brevis digitorum must 
formerly have arisen higher up 
the fore-leg, and have secondarily 
shifted downwards to the dorsum 
pedis. The connection demon- 
strated by Buge between the short 
common flexor of the toes and the 
interossei pedis undoubtedly in- 
dicates the " extreme limit of the 
distal wandering of the extensor 
brevis." 

Buge has further proved the 
interesting fact that all the seven 
interossei pedis at a certain stage 
in the human embryo have a 
plantar disposition, and that they 
shift at a later stage to a position 
between the metatarsals, there to 
divide into the plantar and dorsal 
series. An exact parallel to this is found in certain Apes {Cehtis, 
Cercopithecus) and in most of the lower Mammals, in which 
the Interossei have a plantar position throughout life. In' the 




}. 72. — Superficial Mobcles and 
Tbsdoss of the Dobsum of thb 
BiOHT Foot. One -third natural 
size. (After Bauber.) 

tibia ; i, fibnU ; c, navicular ; tn'., 
tibialie antlcus muscle ; t.n",, its 
tendon of Insertion ; e-C, M. eitensor 
propriua hallucis (e.hall. long.) ; e.iF., 






(e. digit longua) ; «.cf., it 
sioD and insertion an tbe secona me ; 
p.t'„ peroneits terlinsi p.t''., its 
insertion on the fifth meUtarsal 
bone ; s., M. soleus ; p.b., M. 
peroneus brevis ; t.b., M. eilensor 
hallucis brevis ; cbr., extensor brevis 
digitorum ; Ig. anterior annular 
ligament; fc. transverse band of 
the dorsal fascial of tbe foot. 



112 THE STRUCTURE OF MAN 

Chimpanzee and Gorilla they are not so markedly dorsal in 
position as in Ateles, Inuus, and the Orang ; the latter therefore 
are, in this respect, the nearest to Man. 

The adductor hallucis with its caput obliquum and trans- 
versum [usually described as a distinct muscle, the transversus 
pedis] originally forms one mass ; this points back to the time 
when it was more strongly developed, and when the great toe was 
capable of more extensive movement (cf. ante,^. 85). The fifth 
toe also once moved more freely, as is indicated by the opponens 
minimi digiti, which is only secondarily differentiated during 
embryonic life from the mass of the flexor brevis minimi digiti. 
The former muscle is, comparatively speaking, much stronger in 
embryonic life than later, when it may entirely disappear.^ 

MUSCLES WHICH APPEAR OCCASIONALLY, AND MAY BE 

CONSIDERED ATAVISTIC 

In dealing with this group of muscles, we may confine our- 
selves to those which point back to lower grades of organisation, 
through which the ancestors of Man may have passed phylogene- 
tically. I wish to insist on this, since nothing is gained by 
simply labelling muscles " theromorphic," and since, in my 
opinion, in dealing with such muscles, Testut and certain other 
authors have exceeded the boimds of moderation. 

One of these apparently atavistic muscles, the cleido-occipitalis, 
which forms a connecting tract between the trapezius and the 
sterno-cleido-mastoid, has already been mentioned {ante, p. 102). 
To the same category belong certain muscle bundles which here 
and there partly fill up the interval between the pectoralis 
major and the latissimus dorsi. A typical example of these has 
been lately described by my pupil Endres {Anat. Anzeiger, Bd. 
viii. p. 387), the morphological significance of the so-called 
Langer's arch being incidentally discussed. 

A muscle which very rarely occurs in Man is the latis- 
simo-condyloideus (dorso-^pitrochlearis of French authors), an 
appendage of the latissimus dorsi, branching off from the 
latter shortly before it is inserted into the humerus. From 

^ The opponens minimi digiti seems to attain development only in the Chim- 
panzee among Anthropoids. [Incidentally to this topic and to that of the reduc- 
tion and CO - ossification of the penultimate and terminal phalanges of the little 
toe (cf. ante, p. 89), it is interesting to observe that the muscles of the little toe 
are more reduced in the higher Apes than in Man.] 



MUSCULAR SYSTEM 113 

this point the muscle runs perpendicularly along the triceps 
(radiating out into the surrounding fasciae) to the condylus 
intemus humeri, into which it is inserted. This muscle is 
present in all Anthropoids, and is either directly inserted into 
the olecranon or contributes to the triceps. 

Near the sternal line the so-called " sternalis " muscle is 
sometimes found. This is a small bundle, which varies in 
form and in the direction of its fibres, lying ventrad of the 
pectoralis major. It may either be bilaterally symmetrical or 
present only on one side. In the former case, the two muscles 
may cross one another and be continued direct into the sterno- 
cleido-mastoid. 

[Considerable controversy has from time to time arisen con- 
cerning this sternalis. It occurs in some 3 to 5 per cent of 
subjects, and is invariably innervated by the anterior thoracic 
or intercostal nerves. While it has by some been referred to 
a possible origin from the pectoralis major, the rectus abdominis, 
and other muscles, it has by others been regarded as a vestige of 
the panniculus. One interesting variation to which it is liable 
is that of forming a connection between the external oblique of the 
abdominal region and the sterno-mastoid. Parsons has recently 
shown that in Eodents the abdominal panniculus, on reaching 
the axillary border of the pectoralis, divides into a superficial and 
a deep stratum ; and from a very careful analysis of the detailed 
relationships of the panniculus in these animals, he has adduced 
strong reason for regarding the fascial sheath of the human 
external oblique as its modified deep abdominal portion. He 
further gives reasons for believing that the deep part of the 
cervical panniculus has become incorporated in the sterno-mastoid, 
and ultimately regards the sternalis as a vestige of that portion 
of the panniculus which originally connected its deep cervical 
and deep abdominal sections.] ^ 

Between the internal condyle of the humerus and the 
olecranon, in Man, a fibrous band always rims, transversely, 
below the superficial fascia which bounds posteriorly the deep 
indentation in which the ulnar nerve lies. This band corre- 
sponds with the epitrochleo-anconseus muscle, which is constant 
in many Mammals ; it is only occasionally muscular in Man and 
the Anthropoids, and then varies greatly in form and size. It 

^ [Parsons has further simplified matters by suggesting that the pectoralis major 
may be itself a derivation of the panniculus. Cf. Jour. Anat. and Phys., vol. 
xxvii. p. 605.] 

I 



114 THE STRUCTURE OF MAN 

is always innervated by the ulnar nerve. According to W. Gruber 
(St. Petersburg), it was found in about 34 per cent, but, accord- 
ing to Wood (London), in only 8 per cent, of bodies examined — 
a want of agreement which may perhaps be indicative of a racial 
difference. This muscle must be referred back to a time when 
a transverse shifting of the ulna was possible in the ancestors of 
Man, as it now is, to some extent, in many lower animals ; and it 
would appear that after the movements of this bone had become 
limited almost entirely to flexion and extension, the muscle 
gradually degenerated and disappeared. 

Finally must be mentioned the levator claviculse and the 
ischio-femoralis or glutseus quartus, which occasionally occur in 
Man. The latter muscle is constantly present in Anthropoids 
[as the so-called scansorius]. ' 

3. Progressive Muscles 

Attention has already been drawn to the fact {antej p. 97) 
that in certain regions progressive and retrogressive variations 
may occur simultaneously ; and this is nowhere so conspicuous 
as, with the facial muscles. Some of these which are in various 
stages of degeneration have already been referred to {ante, p. 
109). All the other mimetic muscles {Le, by far the greater 
number) appear to be progressively developing, in correlation with 
the increase of the intellect and the correspondingly advanced 
functional activity of their associated nerves. This advancing 
specialisation is indicated in the aberration of certain parts, and 
the foriDiation of new layers of muscle. These changes have 
brought about striking differences between these muscles in Man 
and the homologous tracts in the Lemuroidea, where they are 
simple and comparatively easy to imderstand. We are thus able 
to demonstrate for the mimetic musculature very great variations 
of form and size in both a progressive and retrogressive direction, 
as indeed is the case in all organs which are in the act either of 
suppression or of differentiation, i.e. are not in a definitive 
state. 

Progressive development is especially shown in the muscles 
round the eyes, the mouth, and the nose, and also in those of the 
sub-zygomatic region. 

Euge expresses himself upon the tendency to further develop- 
ment and completion of the human facial muscles, very aptly, 
as follows : — 



MUSCULAR SYSTEM 115 

" A free subcutaneous position, slight relations to the skele- 
ton, and the absence of definite fasciae, offer most favourable 
conditions for the initiation of new combinations. The muscular 
elements can naturally only enter upon new departures in various 
directions for the attainment of a greater fimctional activity, as 
the result of very definite causes. These causes are undoubtedly 
present in Man, and lie in his mental qualities and in the faculty 
of speech. The latter calls the muscles around the mouth into 
activity, and the former seek expression in the play of the 
features. These causes of the differentiation of new facial muscles 
hardly exist in the lower animals, which fact accounts, it appears 
to me, for the absence among them of those signs of progressive 
variation with which we shall become acquainted in the muscula- 
ture of the human face. It may be different, however, in the 
case of variations due to quite other causes. The possibility of 
great variability in the facial musculature of the lower animals 
cannot be denied It 'priori ; nor can we dismiss the objection that 
the few observations which have been made on animals have by 
no means settled what must be considered as the normal condi- 
tion for them. In answer to this, I would, however, emphasise 
(1) the fact that variation in the muscles of animals is rarer 
in the wild state than under domestication ; and (2) the con- 
sideration (to which Dobson has rightly called attention) that 
variation in that most domesticated of all animals, Man, ought 
to be far greater than in animals, which, being subject to natural 
selection, in which the fittest survives, have, in some respects, 
a narrower field allotted to them for modification." 

" The chief factor in the transformation and diversity of form 
of the facial muscles in Man, as opposed to the other Primates, 
is the extensive development of the brain-case. This transforma- 
tion alone is enough to account for changes in those muscles 
which lie upon it. But the development of the brain is closely 
connected with the acquisition of mental powers in Man. The 
development of language has necessarily determined a correspond- 
ing development of the muscles roimd the mouth and nose. If 
we can only demonstrate some slight progressive development in 
these parts something will be gained, for we shall be able to say 
that where the higher development of Man leads us to expect 
more complicated anatomical arrangements, these are actually 
found. Vivacity and diversity of expression of the mouth and 
eye are a peculiarity of Man; they mirror forth the higher 
psychical activity, and can only be acquired by the perfecting of 



THE STRUCTURE OF MAN 




Fra. 73. — Deep Muscles om the Flexob 
Side op the Forearm. Oae-UCth untural 
size. (Att»r Bauber. ) 

The musclea of the upper arm, and the 
BnperGcial musclea of the forearm and 
hand, with the lumbricalea, are removed. 
The position of the auterior annular 
ligament la indicated hy two dotted lines. 

hu,, huments ; p.c., processus coronoideua 
ulnie ; l.o,, the orbicular ligament ; p.a',, 
proc. atyloideua radii ; p.s'., proc. sty- 
loideus ulnas ; e.e., eminentia carpi ul- 



,;J.c..lig. 



uhltimediale: 



. supinator ; /./., M. flexor longus 
pouicia ; /.p., M. flexor profundus 
digitorum ; p.q., U. pronator quadratna ; 
/.ft., deep head of the flexor bravis 
poUicis ; a.p., M. adductor pollicls ; i.p,, 
M. interosseus dorsalis primus ; i.d.. Mm. 
interossei dorsalcs et volarea ; be., 
bicipital tendon. 



the muscles round these organs. 
It is, therefore, a fact of the 
greatest importance that, while 
many variations are found in 
the muscles near the mouth 
and the eyelids of Man, in- 
dicative of new possibilities of 
development, in the other Pri- 
mates these muscles show a 
monotonous constancy. May 
it not also be possible that still 
more subtle differences occur 
between the various human 
races in the detailed arrange- 
ment of the facial muscles ? 
In such a question, however, a 
trustworthy decision can of 
course only be arrived at after 
extended comparative inquiry." 
In addition to the facial 
region, there are three others 
in which progressive muscular 
variations are to be found. 
Taking first the hand, we may 
select for special consideration 
the thumb. We are immedi- 
ately struck by its apparent 
superfluity of muscles.' Our 
attention is specially arrested 
by the long flexor of the thumb 

' For inatance, the abductor pollicis 
haa often a double or even triple 
tendon, and supernumerary tendona of 
the moat various muscles, as if attracted 
by a magnet, often become inserted into 
the thumb (e.g. tendons from the 
bracbio radialis, extensor poUicia longua 
and brevia, extenaor longua radialis and 
extensor digitorum communia). In all 
tbese we probably bave to do witb the 
beginnings of aecondary pi-oceases of 
ditTerentiation, wbich have already been 
indicated in connection with the skeleton 
of the hand {anle, p. 77). 



MUSCULAR SYSTEM 117 

(fl. longua pollicis) (/./., Fig. 73), the diiferentiation of which out 
of the common mass of the flexor profimdua digitorura (f.p.) 
commences in Anthropoids, but is first carried out in Man. 
Not infrequently, however, more often in the lower than in the 
higher races, we iind reversions to the primitive condition, i.e. 
a more or less extensive inter-com- 
munication of fibres of, or even a 
fusion between, the flexor pollicis and 
the flexor profundus. 

This differentiation of the flexor 
longue pollicis, which finds its 
highest expression in the attain- 
ment of independent movement and 
in the greatest possible play of the 
thumb, has its parallel in that of 
the flexor longus hallucis (f.h.. Fig. 
74), which is derived from the flexor 
digitorum communis pedis.' The in- 
terchange between the fibres of these 
two muscles is so very frequent that 
it is hardly ever wanting. Further, 
all the variations observed in them 
are normally met with in Apes, even 
to the diflerent radiations from the 
tendinous anastomosis to the toes.^ Fw. 74.— median Serieb of tbb 
Plantar Muscles, en tbbir 

■ In the Gorilla the flenor digitorum com- Tendons. One -third natural 
lonnia profundus ia subdivided into two portions. size. (After Bauber.) 
The ulnar portion is inaerted into the fiftli, the cl., tuber calcanei ; Ig.. 
fourth, and the middle fingers, the radial one 
into tlie indos finger and the poUex. Testut 
has proved that this condition may rarely 
occur in Man, and that it sometimes occurs 
on both sides in the same individual. In the 
Orang there is only a simple undivided flexor 
digitorum communis profundus without any 
tendon for the thumb This arrangement also 
has been four times observed in Man — in one 
case in a inicroeephalaus individual. 

' The frequent variations in the development of the caro quadrata Sylvii, and its 
occasional entire aljsence, find a parallel in Anthropoids. In the Chimpanzee, for 
example, the muscle is oft«n reduced to a single little fleshy bundle, or may be 
altogether wanting, as appears to be the case in the Orang, Gibbon, and Gorilla. 
In all cases, however, the numerous variations indicate that the caro quadrata 
attained its present position secoudarily, i.e. that it must formerly have lain higher 
up on the calcaneus and the fore-leg ; aud, indeed, an extension of the muscle in this 
direction has been observed. 




ineo - ctiboiiieum plantare ; /./.. 
tendon of fleior longus digitorum ; 
f.h., tendon of fleior longus hal- 
lucla ; td,, tendiuoas connection 
between fleior lougus and adjacent 
tendons ; q-p',, lateral head of 
the M. quad rati plantte Beior 
flccesaoriaa ; ^.p"., its median 
head ; lb.. Mm. lumbricales ; 
/.*'. M. flexor brevia hallucis ; 
/i".,M.flexorbrevis minimi digitl. 



THE STRUCTURE OF MAN 




Fio. 76. — Dbbp Dorsal Musclbs or thb 
FoHBARU. One-fifth natural Bize. (After 
Rnulier.) 

hu, haraernB i til., olecranon process of uln» ; 
rd,, radius ; pr., processua styloideus 
ulnn ; me,, os metocsirpenni secundum, 
a., M. ttuconaiUB ; /.p., M. fleior pro- 
fundus digitorum ; /.c, flexor carpi 
nlnaris, separated ^om tlie fiiscia of the 
forearm ; e.b. , eitensor carpi radialis 
brevior ; e,t., the t«ndon of the eitt 
carpi ndialis loagior ; e.j/., M. 
metocarpi pollicis ossis ; e.p". M. 
primi intemodii pollicis ; cp"'., M. 
aecundi intemod^ pollicis ; e.i., M. eit. 
Jndicis ; e.ni., insertion of the ex 
tendon into the middle flnger, and its 
connection with the second and third 
dorsal interOBSei. 

of the lower Vertebrates these 



We saw above that a num- 
ber of muscles and tendons 
meet in the thumb ; and the 
same applies, though to a lesser 
degree, to the great toe. To it 
offehoots of the extensor hallucis 
longior and the tibialis anticua 
or their tendons pass ; these, 
however, do not indicate the. 
commencement of a new de- 
velopment, but rather a rever- 
sion to a former condition, in 
which the great toe was capable 
of freer movement 

It would be difficult to 
decide to what extent the 
variations which occur on the 
ulnar border of the forearm 
and hand, in the region of the 
extensor and flexor carpi ulnaris 
and the extensor digiti quinti 
proprins, may be the beginnings 
of a progressive development. 
On the other hand, there can 
be no doubt that the changes 
at the fibular border of the 
foot, which have already been 
mentioned {ante, p. 112), are 
degenerations. 

The already described dif- 
ferentiation of a flexor longus 
pollicis and a flexor longus 
hallucis out of the original 
simple flexor masses, finds a 
parallel in the Ontogeny and 
Phylogeny of the superficial 
and deep common flexors of the 
fingers. The two latter are 
connected by an interchange of 
fibres which may amount to 
complete fusion ; and in many 
muscles may not only be con- 



MUSCULAR SYSTEM 119 

nected with one another, but also with neighbouring muscles, 
such as the pronator teres, palmaris longus, flexor carpi radialis 
and ulnaris. The two flexors originally formed (as in the 
lower Mammals) one mass; and in the human embryo they 
still arise as a single blastema, which is only at a later stage 
of development split up by ingrowing partition walls of con- 
nective tissue. 

In Anthropoids these muscles are throughout life connected 
by anastomosing strands, which clearly indicate their former 
union, and to this cause, and the lack of a distinct flexor 
pollicis proprius, is due the less marked specialisation of the 
Anthropoid hand as compared with that of Man. In Man, the 
flexores digitorum communes, superficial and deep, are, as a rule, 
distinct ; but the more or less complete fusion often found 
between them points to the fact that their separation is (geo- 
logically speaking) not of long standing, and has not yet become 
stereotyped. 

The same is the case with the not infrequent fusions 
involving the two radial extensors of the hand, which must also 
be regarded as reversionary. Indeed, these two muscles may fuse 
completely, and, in such a case, we have a realisation of that 
lower condition in which only one single extensor carpi radialis 
externus is present. 

A further instance of progressive development in muscles is 
exemplified by the glutei. These, including the adductors of the 
thigh, show their original unity by frequent blending; and 
very often a more or less complete fusion takes place between 
them and the pyriformis, or between the latter and the gemellus 
superior. Further, the frequent absence of the gemellus superior 
in Man deserves mention, because this muscle is also often 
wanting in the Anthropoids. 

The special development of the gluteus maximus is a charac- 
teristic peculiarity of Man. This muscle has a humble origin 
among the lower Vertebrates, and even in the Anthropoids there 
is nothing comparable in size and strength with its excessive 
development in Man, which is a direct accompaniment of the 
upright gait. The muscle fixes and steadies the pelvis, or rather, 
the whole trunk, on the heads of the femora, and through them 
on the lower limbs, as on a support or stand. 

Closely connected with the assumption of the upright gait 
by Man, which involves the transformation of the former pre- 
hensile feet into ambulatory and supporting organs, is the 



120 THE STRUCTURE OF MAN 

development of the superficial muscles of the posterior surface 
of the fore-leg, i.e. of the calf. The gastrocnemius and soleus 
were formerly as directly connected with the sole of the foot or 
with its fascia as was the plantaris. The terminal tendons of 
these muscles have alike shifted back to the calcaneal tuberosity ; 
but while the plantaris very soon began to degenerate, the soleus 
and gastrocnemius ^ have attained an excessive development speci- 
fically characteristic of Man. We have here another instance of 
retrogressive and progressive changes taking place side by side 
in one and the same region.^ 

Eetrospect 

Gathering together the conclusions which follow from the 
above review of the musculature, we find first that age seems to 
have no influence on the frequency of variation and reversionary 
phenomena. We must, however, except foetal life, since, during 
that period, certain muscles may appear which afterwards suffer 
more or less complete degeneration. 

No definite laws can be framed either as to the disposition 
or division, the symmetry or asymmetry, of the muscles, or as 
to the general condition of the body to which they belong, e.g. 
the strength or weakness of the individual. Correlative changes 
counteracting those due to variation are not observed. It is the 
exception to find that anomalies extend to the homologous 
muscles of the fore- and hind-limbs of the same side. 

Examination of eighteen male and eighteen female bodies by 
Professor Wood at King's College, London (in 1867-68), led to the 
conclusion that anomalies are more frequent in the musculature of 
the limbs than in that of the rest of the body, and that the fore- 
limb is in particular distinguished by their occurrence (292 varia- 
tions were found in the fore as against 119 in the hind-limb). 
It has further been ascertained that variations become more 
frequent as examination proceeds in a distal direction, i.e. as those 
peripheral parts of the body are reached which are more directly 
exposed to the modifying influences of the environment. 

^ A sesamoid bone sometimes occurs near the lateral point of origin of the 
gastrocnemius. In Anthropoids and many other Mammals several such bones 
(fabellfe) are found, one, for instance, at the median point of origin of the muscle. 

^ Various circumstances point to the fact that the biceps femoris, semitendinosus 
and semimembranosus, originally arose higher up than at present, viz. from the 
ilium, and the sacral, or caudal vertebrae. The fact that they have wandered on to 
the ischial tuberosity would appear to be connected with the forward translocation 
of the pelvic girdle already discussed {ante, p. 33). 



MUSCULAR SYSTEM 121 

lu general, the principle holds good that those muscles 
are most subject to variation which can be dispensed with 
without disturbance or disadvantage to the organism as a whole, 
either because they can be easily replaced by other muscles, 
or because they have only a subordinate part to play. In 
illustration of this I would merely refer to the pyramidalis, 
the abortive caudal muscles, the muscles of the pinna, the 
palmaris and the plantaris, the vestigial character of which 
clearly points to their ultimate complete suppression. 

Eesearch has shown, however, that it is not only to the 
retrogressive tendency of the muscles that variation is due, but 
that variation may in some cases indicate a tendency to 
progressive development. The best example of this is aflforded 
by certain flexor muscles, and by the flexor longus poUicis, and 
the gluteus magnus. 

A third kind of variation occurs, in those cases in which a 
tendon may return to former points of insertion on neighbouring 
bones, e.g. the rectus abdominis is occasionally inserted on to the 
more anterior ribs. And to the same category belong the 
splitting off of the abductor hallucis from the tibialis anticus, 
which occurs in very varying degrees. 

All these cases, which must be denominated reversionary, 
indicate the extraordinary tenacity with which certain 
peculiarities persist and are repeatedly passed on from one 
generation to another. This power of reproduction must, however, 
necessarily grow weaker, as an organ in course of time loses its 
original functions in adaptation to new ones. As a consequence 
of this, attempts at reconstruction necessarily become more and 
more imperfect. 

The same is the case with many other muscles {e.g. the 
sternalis, levator claviculae, latissimo-condyloideus, and epitrochleo- 
anconaeus) which now only rarely occur in Man, and which, when 
they are present, furnish important indications of a long-past 
period in the development of the human race. 

There is no good ground for doubting the possibility of the 
hereditary transmission of muscular anomalies, although, as Testut 
rightly remarks, the difficulty of obtaining material for a direct 
proof is evident. The difficulty in this case is greater than in 
that of mere external variation, such as pigmentation, different 
coloration of the opposite eyes, abnormal hairiness, birth-marking, 
Polydactyly, and others akin to these. 

It is reserved for future investigators to add to our as yet 



122 THE STRUCTURE OF MAN 

scanty knowledge on this subject, by using more fully the material 
which the different human families and races could afford us. 
It is not impossible that some of the views till now held, e.g, 
that Negroes and other low races do not differ specifically in their 
myology from the Caucasians, and do not show more frequent 
variations, may have to be modified. 

Anthropotomy has here a great field. On the other hand, 
the mass of recorded observations upon muscular anomalies in 
general is so great, and the agreement of many of these with 
the condition normal in Apes is so marked, that the gap which 
usually separates the muscular system of Man from that of the 
Anthropoids appears to be completely bridged over (Testut). 



THE NEEVOUS SYSTEM 

Throughout the animal kingdom the nervous system is more 
conservative in character than any other, and it thus offers a 
more limited field for the study of vestigial structures. The 
latter, however, as we shall see, are not altogether wanting; 
indeed, they may be here of special interest, as they afford the 
best proof of the extreme tenacity with which an organ, or some 
part of an organ, may persist and be transmitted through an 
immense period of time, when its functional activity is to a 
marked degree reduced, or even no longer evident. 

The central nervous system of the Vertebrata, as is well 
known, arises from the so-called medullary folds of the outer 
germinal layer, and is thus essentially a modified derivative of 
the epiblast — the so-called " sensory layer." The latter, in the 
lower animals, e.g, certain Coelenterates, in which there is no 
sharp differentiation into a central and a peripheral nervous 
system, remains superficial in position and is directly the medium 
of communication with the external world. This, combined with 
the fact that, in Vertebrates, the brain and spinal cord are among 
the first differentiated organs, is a distinct proof of the great age 
and physiological importance of the nervous system. 

The Spinal Cord 

When first differentiated, the nervous axis, as already men- 
tioned, corresponds in extent with the axial skeleton; but it 
soon appears to shorten, partly from inequality of growth, and 
partly in consequence of modification taking place in the posterior 
portion of the vertebral column. The spinal cord no longer 
extends throughout the whole length of the vertebral canal, its 
posterior tapering extremity [i.e. the portion caudad of the spinal 
nerve -roots, where tlie filum terminale begins] reaches no 
farther down [in Man] than to about the boundary between the 



THE STRUCTURE OF MAN 

thoracic and lumbar portions of the column. 

sA, This shortening, as above said, is more 
apparent than real, for the vertebral column 
[growing the more rapidly] extends farther 

li^ and farther back beyond the posterior 
limit of the spinal cord. [It is worthy of 
remark that this ineqiiality of growth, so 
marked in Man, is still more conspicuous 
among certain lower Mammals — e.g. the 
Hedgehog, in which the filum terminale 
commences in the anterior thoracic region.] 
Tlie filum terminale {f.t., Fig. 76) 
runs through the lumbar and sacral 
regions of the vertebral column into the 
caudal ; and this terminal filament, which 
grows with the growing vertebral column, 
is the vestigial homologue of the posterior 
portion of a spinal cord which, in the 
ancestors of Man, may have run evenly 
throughout the whole length of the 
vertebral column, as it now does in many 
lower Vertebrates. This process of reduc- 
tion, which sets in at the posterior end of 
the spinal cord, is profoundly significant, 
as we have already had to describe a 
similar process of reduction going on at 
the posterior end of the axial skeleton itself 
(ante, pp. 28 et seq.). 

1 should like to suggest the consideration 
wliether certain pathological conditions may not 
be traced to this source, it only indirectly? I 
refer to those frequent diseases of the spinal cord 
known as tahetic, which in by far the greater 
number of cases arise at its posterior end. May 
not the above described condition of the lumbar 

FiQ 76.— LowKn Portion op the Spinal Coed, with the Cauda Equina and thk 
Enveloping Duha Mater. (Dorsal aspett.) One-half natural siie. (After 
Sohwalbe, ) 

The dura niatral sheatli has been openeil up from beliind and laid back ; on the left side 
the root? of the nerves are represented entire ; on the right, the lower of these are 
shown removed above their passage throngh the sheath, and the bones of the coccyx 
are delineated in tlieir natural relative positions, in order to show the relations of the 
filum temiinale suil the coccygeal nerves. 

cc, coccygeal nerves ; f.s., dorsal longitudinal fissure ; /.I., filum terminale. slightly dis- 
placed to the right side ; (6. i aud v, first and fifth lumbar nerves ; l.d., ligamentnni 
denticiilatuin ; sc. i and v, first and fifth sacral nerves ; «A., the ducamatral sheath ; 
fA. I and xii, tenth and twelfth thoracic nerves. 



THE NERVOUS SYSTEM 125 

portion of the mj^elon be considered as a predisposing factor in the 
degenerative processes apparent in such cases ? A parallel to this occurs, 
it seems to nie, in the processes of reduction at the upper part of the 
thorax already mentioned (ante, p. 43), and in the pathological processes 
which set in at the tips of the lungs, perhaps connected therewith. 

That there are also jprogressive processes going on in the 
human spinal cord is probable, from the following observations 
made by Lenhoss^k on Mice, Guinea-pigs, Eabbits, and Cats. In 
these animals the pyramidal tracts are much more feebly developed 
than in Man (in whom they attain their highest differentiation), 
and their position in the spinal cord varies greatly. In the 
Guinea-pig, Mouse, and Eat, they run in the dorsal columns, in 
the Eabbit, the Cat, and other Carnivora, in the lateral, and in 
Man, partly in the lateral and partly in the ventral columns. 
This may perhaps be indicative of a gradual shifting of these 
tracts from the dorsal to the ventral columns, as we pass from 
the lower to the higher Mammalia ; and it would be interesting to 
investigate this point in the Apes. Even in Man the definitive 
condition is not reached, for the fact that the pyramidal tracts 
may run either along the ventral or the lateral columns is 
evidence that they are still subject to variation. 

» 

Since the pyramidal tracts cross one another completely 
in all animals which have been examined, it seems likely that 
their alleged semi-decussation in Man is only apparent, as the 
elements of the ventral tracts do eventually cross one another. 
And further, since these ventral tracts are wanting in Man in 
fifteen cases per cent, it would be necessary, if belief in semi-decus- 
sation is to be persisted in, to consider that a certain number 
of individuals were remarkable exceptions in that important 
character. Inasmuch as this supposed variation is unaccompanied 
by exceptional conditions of other parts of the organism, it is 
altogether improbable that it exists. 

I must refer the reader to the works of Waldeyer for an 
account of the differences to be found between the human spinal 
cord and that of the Gorilla. 

Before turning to the condition of the brain, attention may 
be drawn to a small body which lies beneath the last coccygeal 
vertebra, known as the coccygeal gland. This, on account of its 
close relation to the arteria sacralis media, is usually, but, it 
seems to me, incorrectly, relegated in text -books of human 
anatomy to a connection with the vascular system. Considering 
the established fact that the caudal end of the spinal cord, at an 



THE STRtTOTURE OF MAN 



early period of development, reached exactly to that point at 
which the coccygeal gland is found later, and that, aa already 




Kio. 77.— Brain o? a Doo-fish {Scytlam eankxda). 
A, dorsal ; B, ventral ; C, side view ; b.o., bnlbns olfactorius ; (p., pineal gland cut alrort ; 
/.*., fore-bralu ; /.r., fossa rliomboidalis ; h.b., hind-braiu (cerebellum) ; hp., hypo- 
phyeia ; i^., infuudibulum ; 1 to x, first to the tenth cranial nervea {the thalamea- 
oephalon and the fossa rbomboidalis are in life covered bj epithelium (plexus 
chor[oidi<i). Dot delineated ; the ventral vagus roots are omitted from Fig. B) ; 
m.d., medulla oblongata; m.h., mid-brain (optic lolies) ; sc., saccus vasculoaus ; 
t.0., tractus otfactorins. 

mentioned, all the important variations at the caudal end of the 
trunk are primarily associated with degeneration of the spinal 



THE NERVOUS SYSTEM 127 

cord at that region, I am inclined to think that some connection 
exists between the latter and the coccygeal gland. This gland 
is undeniably a vestigial organ, but we have as yet no certain 
knowledge of either its significance or its primitive history. 

Brain 

The himian brain, in the course of its development, passes 
in regular order through conditions characteristic of certain of 
the lower Yertebrata (ex. disposition of the cerebral vesicles, 
smooth surface of the hemispheres), and these lower con- 
ditions are in rare cases retained, as in many microcephalous 
individuals, as the probable result of arrested development. 
There are not infrequent deviations from the normal arrangement 
of the cerebral furrows and convolutions, which are closely con- 
nected with the development of the gray matter. These 
deviations can be best studied by the aid of Comparative 
Anatomy and Ontogeny, and the same may be said of the 
posterior cornu of the lateral ventricle, the calcar avis, and 
the eminentia collaterals Meckelii. Conspicuous among variable 
cerebral furrows we note the parieto-occipital fissure (/.^o.. Fig. 78), 
which is occasionally very pronounced. This fissure runs out 
laterally, and may probably be a reversion to the pithecoid type 
(it is called in German the " Affenspalte "). In its normal 
condition it seems almost to be vanishing, as compared with its 
supposed homologue in the brain of the Ape.^ 

In spite of difference in detail, there is a closer general 
resemblance between the human and the Anthropoid brains than 
between the brains of any other two Vertebrate groups. 

With regard to the weight of the brain in Anthropoids 
generally, the material as yet examined is not sufficient for the 
determination of averages and formulation of general conclusions. 
With the Chimpanzee, however, this is not the case, as a rela- 

^ [The tenn parieto-occipital fissure insufficiently defines this supposed homologue 
of the *' Affenspalte.** Cunningham in a recent elaborate treatise {Cunningham 
Memoirs f vii E. Irish Acad.^ 1892) has devoted much attention to this topic. He 
and other leading authorities are agreed that, whether the " Affenspalte " of the Ape 
is present in the human adult or not, the **fissura perpendicularis externa" of the 
f(]etus is its homologue. During the passage of these pages through the press, 
Benham, in a very careful study of the Chimpanzee's brain, has shown {Qu, Jour, 
Micr, Sci,, vol. xxxvii. p. 47) that the transverse occipital fissure which replaces this 
external perpendicular may be genetically related to it, and that therefore Ecker's 
original view that the "Affenspalte" of the Ape is represented in the adult human 
bi-ain by that which he termed the "sulcus occipitalis transvei-sus " may be correct.] 



128 THE STRCCTUEE OF MAS 

tivelj large number of specimens have bees examined ; and 




PlO. 78. — CEBEBBCH op a FBHILB CB[I■PA^EBE TWO TUBS OLD. (Dorsal 

aspect.) (Showing Asj mmetnciil Deielopment.) 

'., ciT., aDterior and postciior central cod volutions f.L, iat«rp«ictal fissuTe ; / 

the longitudinal fisaare ; /.p.o., psjieto occipital fl^ore ; /r., frontal lobes ; i 

occipital lobes ; s.c, snlcns centralis 




Fio. 76. — Brain of a Fejiale Ciuiipaszeb ttco tbabs old. (Lateral aspect.) 
cb., cerebellum ; c.c'.. c.c", anterior and posterior central convolutions ; fr., frontal lobe ; 
/.9., fissura Sylvii ; is., island of Reil ; lad., medulla oblougata j oc., occipital lobe ; 
pa., parietal lobe ; s.c, sulcus centralis ; tp., temporal lobe. 

further, a review of the facts known concerning the Gorilla 
and Orang reveals statistics which may be of use to future 



THE NERVOUS SYSTEM 129 

investigators. For details on this subject I -must, liowever, 
refer the reader to the works of MoUer and others.' 




Fia. 81. — Cbeibbum 




I UUUAN EmBRTO in TBI 
(Doisal Aspect) 
References ag for Fig. 7S. 



' Joh. Mbller, Abhamilg. d. Zool. u. Anlhrop. SOauil. Museums zu Ih-esden, 
1890.1891, [Cr. atao D. J. Cunninghitiii, Cunningham Meiiudn, R. Iriak Acad., 
No, II., 1889 ; No, VII., 1892 ; and Benham, op. eit. In thase works the literature 
or the subject will b« found. ] 



130 THE STEUGTURE OF MAN 

If we take the average weight of the body of a Chimpanzee 
from two to four years old as 8^ kilogrs., and the average weight 
of brain as 343 gra, we shall have 1 : 24-7 aa the relative 
weight of the latter. An Orang of the same age appears to 
possess a rather heavier brain (1:22'3 or 340:7600). A 
comparison of these two Anthropoids with Man, the ratio of 
whose brain weight to his body weight between the second and 
fourth years ranges from 1:18 to 1 1 16, shows that the 
difference at this age is not great, as would seem natural when 
we reeaR the greater similarity to human beings shown by 
young Anthropoids. In older Chimpanzees (90-106,6 em. long) 




K UUHAN EUBBTO S 

[Lateral View.) 
References as for Pig. 79. 

the relative brain weight ia markedly lower, viz. 1 i42,5 (391 : 
16650) or 1:52 (375,6:19500). It is probable, however, 
that the average brain weight in older Chimpanzees is con- 
siderably lower, as in a body weighing 28 kilogra it sealed 
1 : 75. If 'this is the case, a comparison with an adult human 
being, in whom the average brain weight is 1:40-35, shows 
that the brain of Man is relatively at least twice as heavy as 
that of the Chimpanzee, and absolutely three or four times 
as heavy. We learn from this that the brain of the Ape, unlike 
that of Man, develops little with age, and attains its definitive 
condition far sooner. 

The Chiinpanzee and the Orang appear to have approxi- 
mately the same brain weights, but the Gorilla stands markedly 
distinct from them, its body being fiir larger, while its brain 
does not correspondingly increase in size. The weight of the 
body of an adult Gorilla being taken at 94-95 kilogrs., and the 



THE NERVOUS SYSTEM 131 

brain weight at 425,25 gra, the relative weight of the latter 
would be 1:220 (MoUer). 

A comparison of the cerebral surface shows that Man 
difiera from the Anthropoids in the preponderance of the 
frontal lobe (Jr., Figs. 78-82) and, to a lesser degree, of the 
occipital lobe (oc.), and in a corresponding backward extension of 
the temporal lobe {tpl). The parietal lobe {pa.) is about equally- 
developed in the brains of Man and of Anthropoids (Mbller). 

Since this subject has so far been, comparatively speaking, 
little investigated, and since our knowledge of the functional 




Fia. 83.— Hypothbhcal Medun-LonqitudinaIi Section tehouqh the Skull 
AND Bbaih op a Vebtbbbatb Embrto. (Partly after Hmlej.) 
cr'., basia craaii ; ck., chorda dorsalis ; a''., roof of the skntl ; no., Dasal cavity ; c.k., 
cerebral hemiaphere, with the carpns striatum (c.s.) lying basally, kai. the olfactory 
lobe {ol.) anteriorly ; f.b., thalarueucephalon (fore-brain), which has been prodnced 
dorsalty into the pineal gtaad {sp-), and basally into the Infundibuliim [i/.), hp., the 
hypophysis. Anteriorly, the base of the optic nerve {op.) is seen, and in the lateral 
widl the position of the optic thalamus is indicated {th.) ; c.p., posterior commiasure ; 
m.b., mid-brain ; k.b., hind-brain ; cc, canalis centralis. 

significance of the different regions of the brain is still far from 
complete, no general conclusions as to the possible correlation 
of these differences with mental peculiarities can be drawn. 

The slight projection of the cerebellum from below the 
edges of the occipital lobes in Anthropoids, is due less to the 
narrowness of the latter than to the striking breadth of the 
cerebellum itself (Moller), Even in man the occipital lobes do 
not always completely cover the cerebelltun, but in this matter 
considerable variation occurs.' 

Special interest attaches to the pineal gland (epiphysis cerebri) 
(ep.. Figs. 84 and 86) which arises in the region of the roof of 
the fore-brain. 

In the lower Vertebrates this organ either lies free or ia 
embedded in a depression or foramen (parietal foramen) of the 
' It must be loft to future investigators to prove whether the topography of the 
course of the fibres in the optic chiosma given by Joh. Moller for Anthropoids, i.t. 
the constant occuireDce at the surface of certain groups of fibres, has a parallel in 
Man (perhaps in embryos or the lower races). 



THE STRUCTURE OP MAN 



skull roof. lo Man and Mammals the pineal gland is pushed 
away from the free surface of the hrain by the growth of the 
hemispheres, and it is thus shifted back till it comes to lie in a 
depression between the corpora quadrigemina (nates). It is irx 




Fio. 84.— Brain op a Rabbit. 
A. dorsal; B, veutTBl ; C, lateral riew ; b,o., balhiu olfactorius ; cA'., median lobe of the 
cerebellum (superior rermis) ; cb"., its lateral lobe ; cr., crura carehri ; ep., gUodnk 
pinealia ; fJ)., fore-brain ; f,p., Gssunt pallii ; h.b,, bind-brain ; k.p., bypophyaii ; 
i to lii, Arat to the twelfth cranial nerves ; m,6., mid-brain ; md., mednUa oblongata ; 
p.v., tegioD of the pana. 

this position recognisable,in Man, as the well known dorso-ventrally 
compressed pine- or cone-shaped organ. Into it the lumen of the 
third ventricle irequently extends ; and its base divides into two 
stalks, which pass directly into the tieniie medullares and thalarai 



THE NERVOUS SYSTEM 133 

optici. The pineal gland of Anthropoids is identical in appear- 
ance with that of Man. 

The pineal gland in Man is remarkable for its rich vascularity 
and for its cellular follicles, in which concretions (brain sand) may 
develop. 

This " gland " has all along claimed the special attention of 
morphologists ; and as great difficulty has been found in under- 




(icle ; « 



B H TH 


Pink Or n a Rbptilb 


agn d 


A a. p«i.c«r.) 




Kan d with fluid; 


blood.y^seU 


; en., cells in the nerve stalk («.t 



standing it, it has received very different explanations. It is 
only in recent years that light has been thrown upon it by 
numerous works devoted to its comparative anatomy and 
ontogeny. It has been proved that, in close connection with the 
actual stalk of the gland, there is a second vesicular outgrowth, 
which, in certain Vertebrates, shows undeniable traces of being 
a rudimentary unpaired organ of sight. [This organ is now 
known to arise during development in all classes of Vertebrates], 



134 THE STRUCTURE OF MAN 

and to have undergone degeneration in the course of Phylogeny, 
as the roof of the skull became more and more solid. The nerve 
belonging to it is, so far as is known, most fully retained in 
certain Eeptiles. In some animals this organ only occurs in the 
embryo, and altogether disappears at a later stage. 

In examining the finer histological structure of the pineal or 
parietal organ in the Lizard-like Eeptiles and the Slow-worms, we 
find the upper wall may in many cases become thickened to 
form a transparent epithelial plate (r".. Fig. 85), which is often 
lens-shaped, while the rest of the epiphysial vesicle (r'.), which is 
often flattened, is differentiated into a multilaminar "retina." 
" Lens " and " retina " thus arise in complete continuity out of one 
and the same structure ; and it is only at a late stage in develop- 
ment that a more or less distinct demarcation between them is 
effected (B^raneck). The organ is invested by a capsule of 
connective tissue (cp.). 

In many cases the skin which overlies the parietal organ, as 
well as the connective and dural tissues below it, remain free from 
pigment, indeed they are sometimes so clear and transparent that 
they might be considered as a kind of cornea. This justifies the 
assumption that the function of the organ may not be altogether 
lost even now.^ Owsiannikow claims to have found traces of a 
vitreous body within it. 

According to Leydig, Selenka, and others, there is found in 
the embryos of various Vertebrates (Selachians, Eeptiles, Mar- 
supials, and probably in others) another unpaired dorsal appendage 
of the fore-brain, for which Selenka has suggested the name 
" frontal organ " or " paraphysis." 

Whereas the epiphysis grows forward, the paraphysis, which 
arises much later ontogenetically, grows backward and, when the 
epiphysis is once fixed in the epidermis, pushes itself in under 
that organ, so that the parietal eye comes to rest on the para- 
physis as on a cushion. Until the embryo is matiu-e, the 
epithelial tube of the paraphysis remains hollow and in open 
communication with the cavity of the brain. 

If it be established that the pineal organ and gland are 
really sui generis, distinct in origin, there is evidence of three out- 

^ [In view of the intimate relationship between birds and reptiles, it is an 
interesting circumstance that Klinckowstrom has discovered in embryos of certain 
of the former {Anser, Larus.) a "brow spot," which in its structural differentiation 
suggests not only the last trace of a pineal organ, but a pineal scale like that of 
living lizards. Spengel's Zoolog. Jahrh., Anat. Ahth, Bd. v. p. 177.] 



THE NERVOUS SYSTEM 135 

growths from the roof of the brain, of which one, the pineal 
organ, can with certainty be regarded as originally a sense organ. 

[Locy, from the study of young shark embryos, has adduced 
reason for believing ^ that, at an early stage in development, two 
pairs of accessory optic vesicles appear, concurrently with those 
giving rise to the retinae of the paired eyes. The ultimate fate 
of the former has yet to be fully worked out, and nothing is 
as yet known concerning the post-embryonic development of the 
paraphysis. There is, however, reason for thinking that the 
latter probably takes part in the formation of the choroid plexus ; 
but whether this is the case or not, Locy's observation seems to 
indicate that the pineal organ at least may have been originally 
paired.] 

At the under surface of the thalamencephalon, and connected 
with the infundibulum, there lies an appendage of the brain called 
the hypophysis or pituitary body. 

Two distinct structures enter into the formation of this 
organ, one glandular and the other nervous. The former arises 
in Man and the higher Vertebrates by a constriction from the 
primitive mouth sac (stomodseum) of the embryo, and the latter 
is, as a rule, assigned genetically to the floor of the thalamen- 
cephalon. Future research must show how far this is the primary 
origin of at least the glandular portion of the organ, and this is 
the more desirable since some very interesting results recently 
obtained by von Kupfifer, from the study of Lamprey and Sturgeon 
embryos, have given new zest to the inquiry into the primitive 
history of this enigmatical structure. The subject cannot be 
dealt with in detail here, but mention may be made of at least 
a few of the chief points concerning it. 

According to von Kupfifer, the hypophysis arises in the 
above-named Fishes in the manner described by Scott for the 
Amphibia {Amhly stoma). At a very early embryonic stage an 
ectodermal cell-strand grows in from the anterior region of the 
head. This cell-strand in the Sturgeon consists of two closely 
applied epithelial plates which form a fold, and at the point 
at which it arises the antero- dorsal border of the fore-brain 
is connected with a thickened portion of the ectoderm by an 
originally hollow and subsequently solid tract. This ectodermal 
thickening is termed by von Kupfifer the median olfactory 
plate, and the corresponding cerebral outgrowth the lobus 
olfactorius impar ; in fact, according to this author, the Sturgeon, 

^ [Anat. Anzeigpr, vol. ix. p. 169.] 



136 



THE STRUCTURE OF MAN 



during its earliest development, passes through a monorhinal 
stage, and probably more or less distinct traces of this can be 
discovered in the embryos of all Vertebrates. 

From this median or unpaired olfactory plate, therefore, 
which may be homologous with the anterior neuropore of 
embryologists, and with the " olfactory organ " of Amphioxus, the 
hypophysial tube arises, prior to the formation of the mouth, and, 
growing down gradually, approaches the base of the brain till 
it reaches the neighbourhood of the infundibulum. The epithelial 
strand later separates off from the ectoderm, and finally to a great 



€)). 




Fig. 86. — Median Longitudinal Section through the Head of a Newly - 
HATCHED Larva of the small Lamprey {Petromyzon pUmeri). 

f.h,^ fore-brain ; m.h., mid-brain ; h,h., hind-brain ; ep., glandula pinealis ; U., olfactory 
organ; hp., hypophysis; st,y buccal sac (stomodaeum) ; aZ., endodermal cavity 
(mid-gut) ; ch., chorda dorsalis. 

extent degenerates, so that at last nothing remains of it but its 
constricted, swollen end — the glandular hypophysis of adult 
anatomy. A somewhat similar arrangement is seen, as has 
already been said, in Ammoccetes and certain tailed Amphibians. 

The facts appear to me strongly to confirm the view that 
the hypophysis corresponds with the primitive mouth (archi- 
stoma) of the ancestors of the Vertebrata. 

The present vertebrate mouth (neostoma) is by some considered 
to have arisen by the running together of a pair of branchial 
clefts ; but this is by no means definitely proved. 

According to Scott, the close connection between the hypo- 
physis and the oral invagination (stomodaeum) of the higher 
Vertebrates was developed secondarily in consequence of cephalic 
flexure, due to the preponderating development of the fore-brain. 
If so, the hypophysis had originally no relation either to the 
mouth or the nose, but is to be regarded as an organ (? sensory). 



THE NERVOUS SYSTEM 137 

inherited from a supposed invertebrate ancestor, which originally 
had the form of a blind sac on the free surface of the head, close 
to the olfactory organ. Scott and von Kupflfer thus differ con- 
siderably in their views ; [but whatever the original significance 
of the hypophysis, all observers are agreed that it is the vestige 
of an organ originally distinct from the present vertebrate mouth 
and from the nose of at least the gnathostomata. With respect 
to it, the Vertebrata collectively fall into two distinct and diversely 
modified assemblages, viz. (i.) the Epicraniata (Lampreys and 
Hags), in which it is carried up with the nose and perforates the 
basis cranii from above ; and (ii.) the Hyjpocraniata (Fishes 
proper. Amphibians, and Amniota), in which it is carried down 
and inwards with the mouth, and perforates the basis cranii from 
beneath.] 

We still have to consider those cases in which degeneration 
of the brain is either beginning or has made some progress. 
We find an instance of commencing degeneration in the lobus 
olfactorius, to which we shall have to return when considering 
the olfactory organs. A case of advanced degeneration is seen 
in the roof of the fourth ventricle. This, in Man, as in all 
Vertebrates, becomes almost entirely transformed in the course of 
Ontogeny into a vascular membrane, overlying a simple epithelium, 
and continuous laterally and anteriorly with the pia-mater. The 
lining epithelium is continuous laterally and posteriorly with the 
delicate structures bordering on the calamus scriptorius known as 
the obex, ponticulus, and ligula (taenia). These all consist of 
nervous tissue, and are to be classed morphologically with the 
epithelial layer just mentioned. The rudimentary character of 
the series is evident, and the same applies to the velmn medullare 
posterius. 

In contrast to the degenerate portions of the brain, other 
parts are found to be in course of progressive development ; these 
more than compensate for the loss not only of the above 
mentioned, but of all other degenerating parts. We have only 
to mention the cerebrum, with its continually developing com- 
plexity of the nerve tracts, especially the complex components of 
the gray cortex, which, as the organs of the mental faculties, are 
kept in constant touch with the surrounding world by means of 
the centripetal and centrifugal tracts of the peripheral nervous 
system. 

To this topic we shall have to return. It will here suffice 
to mention one more portion of the brain in which variation in 



138 THE STRUCTURE OF MAN 

form and size are evident to the naked eye, and are, I consider, 
to be interpreted as progressive. This is the lobus occipitalis 
of the cerebral hemisphere, in which we find great variation 
in the extent of the calcar avis, and the posterior cornu of 
the lateral ventricle. Exact statistics on this subject are a 
desideratum. 

[In connection with the question of structural degeneration of the brain, 
certain recent observations of Forsyth-Major are of especial interest. It has 
been generally assumed that the smooth cerebrum and exposed cerebellum of 
the Lemurs, which are placed at the root of the order Primates of which Man 
is the highest member, are primitive characters, indicative of a relationship 
with and origin from a lowly order of Mammals. Forsyth-Major has discovered 
evidence of structural simplification and degeneration, during Ontogeny, of 
the brain of certain Lemurs (apparently in correlation with preponderating 
development of the face and nose) which points to the conclusion that the 
supposed primitive characters named may be secondary and retrogressive — 
a welcome suggestion, in view of Cope's discovery that the oldest known 
Lemurs (Anaptomorphidae) had large and highly -organised brains. The 
brain of the human foetus, at from three to five months, develops certain 
convolutions which are early lost and have nothing to do with those of the adult. 
Kolliker, Beer, Cunningham, and others have investigated them, and the 
latter, suggesting that they may be the expression of mechanical effects conse- 
quent on a "quadrupedal growth pause" in development, has proposed to 
term them " transitory fissures " (microgyri of Beer). Considerable interest 
attaches to the occasional appearance of convolutions upon the surface of the 
hemispheres in normally smooth-brained Mammals ; as also to the question 
whether these are progressive structures, or conversely, whether they, and 
the convolutions which seem to disappear during Ontogeny among the 
Lemuroidea, may have anything to do with the ** transitory fissures " above- 
named. A wide field of inquiry is here opened up, which gives promise 
of most important results.] ^ 



Peripheral Nervous System 

But few retrogressive phenomena are here met with ; among 
these are the present condition of the rami recurrentes of the three 
branches of the trigeminus and of the vagus, which run to the 
dura mater, and further, of the ramus auricularis of the latter nerve. 

The fact that in the region of the hypoglossus vestiges of 
the posterior roots with their ganglia have been found in human 
embryos, as they were long since in certain lower Mammals, 
indicates that assimilation of spinal or vertebral elements may 
be going on in the occipital region of the skulL Certain delicate 
nerve loops which lie in the region of the trigeminus, facialis 

^ [Cf. Foi'syth-Major in Rothschild's NomiaJtes Zoologicce^ vol. i. p. 35 ; and Cun- 
ningham, Cunningham Meinoirs, R. Irish Acad., No. VII. p. 30.] 



THE NERVOUS SYSTEM 139 

and glossopharyngeus nerves, or are connected with their ganglia, 
may possibly be retrogressive in nature; but we cannot enter 
further into their study here, as to do so would lead us too far 
into Comparative Anatomy, and be beyond the purpose of this 
work. 

The variations which are continually taking place in the 
brachial and lumbo-sacral nerve plexuses, in connection with the 
shifting of the limbs and their girdles during development, have 
been already considered in detail {ante, pp. 95 and 96). 

The Sympathetic System 

Here also extraordinary variations are to be found in the 
form, number, and size of the ganglia of the main trunks, in the 
peripheral plexuses, and in the connections between the two chief 
trunks ; but, except in the caudal portion of this system, we are 
not justified in assuming that we have to do with retrogressive 
phenomena. 



THE SENSE OEGANS 

The sense organs have always been classified into lower 
and higher, and that not without justification. Conspicuous 
among the lower sense organs are those of the tactile sense lying 
in the integument ; and by the higher sense organs are under- 
stood the olfactory, visual, auditory, and gustatory apparatus, 
which are located in special depressions or cavities of the 
head. 

It may now be considered as certainly established that all 
the latter may be traced back phylogenetically to tegumental 
sense organs, and that their sensory epithelia are to be regarded 
as modified epidermal derivatives. 



Integumental Sense Organs 

It appears to me not improbable that the tactile bodies which 
are profusely scattered throughout the integument of man are 
genetically closely connected with his gradual loss of hair. I am 
led to this conclusion by the fact that tactile bodies appear 
in the lower Mammals principally, indeed, perhaps exclusively, 
in places where there is no hair (proboscis, entrance to the mouth, 
plantar surface of the paw). They appear unnecessary in hairy 
parts of the body, because the hairs themselves, being richly 
provided with nerves, are capable of exercising a delicate tactile 
function. 

How far certain epithelial structures proved by Maurer to 
exist in the hair germs are to be deduced from phylogenetically 
older tegumental sense organs like those of the Anamnia, must 
be established by further investigation (compare also the already- 
mentioned temporary appearance of sense organs in the cephalic 
region in embryos, ante, p. 133). 



THE SENSE ORGANS 



The Olfactory Organ 



The Nuwher and Structv/re of the Olfactory Eidges 
and the Turbinals 

Following Broea and Turner, we may divide Mammals, accord- 
ing to the development of their olfactory apparatus, with especial 
reference to Its cerebral portion [" rhineneephalon," " lobe lim- 
bique "] into series, viz. r 

[i. Osmatic series, turbinals present and usually five in 
number.] 

(a) Macroamatic [organs of smell largely developed], (most 
Mammals, e.g. Edentata, Ungulata, Carnivora, Eodentia, Mar- 
supialia, and Lemuroidea). 

(6) Microsmatic [olfactorj' apparatus relatively feeble] (Pinni- 
pedia. Whalebone - Whales, 

Apes, Man, and Monotre- ? ^■ 

mata). 

[ii. Anosmatic series, or- 
gans of smell, apparently 
absent in the adult] — (Dol- 
phins and Toothed - Whales 
generally, although many of 

these require further investi- „ o, t »,^ \ ■<■. v 

'■ Fio. 87. — Lateral view of the Nasal 

gation with regard to this Chamber of a Hvum Embbto. 

Dointl ^ ^' ^^' ■'"' "** three olfuctorj' ridges ; 

" '' . it, sopernumerary ridge which occurs in 

The first point to be the embryo; n., tip of the nose; pi., 

established is the primitive hard piJ»te; cr., haae of the skull j ■«.. 

'^ ostmm of the Eustachian tube- 

number of the olfactory ridges. 

The investigations of Zuckerkandl lead to the conclusion that 
the original number of these ridges was comparatively small, and 
that where, among Mammals, we have a large number or a 
more complicated form of turbinal, they have been secondarily 
acquired in the interest of a greater physiological efficiency. 

Most orders of Mammals, e.g. the greater number of Carnivora, 
Rodentia, Insectivora, Lemuroidea, Marsupialia, with Ornitho- 
rhynchus {Echidna f), have five olfactory ridges ; but the Ungulata 

' [Kukentbal baa recently worked out the development of the olfactory organ in 
the Delphinidie, and has proved (i) that the nnion of the external naeal apertures 
ia a secondary process occurriog during Ontogeny, and (il) that in the young embryo 
we II- developed olfactory lobes and bulbs are present which disappear in the adult. ^ 
Dcnksch. d. Tntdic-natur-iom. Oetellsch., Jena, Bd. iii. pp. S29 et aeq.] 




143 



THE STRUCTURE OF MAN 



have, as a rule, more than five, and sometimes as many as eight. 
The Edentata possess from six to eleven (Orycteropus has eleven, 
Dasypus nine, Bradypus and Mania seven, Myrmecophaga six), 
and the Primates from one to three. 

At a late emhryonic period three olfactory ridges are often 
present in Man, inasmuch as between the superior and inferior 
a third projects into the lumen of the nose (cf. Fig, 8*7). 
This last, when present, is more or less distinct at birth, but 
it becomes reduced later, the superior ethmo-turbinal, as a 
rule, growing over it like a cover. With this superior ethmo- 
turbinal, which must be considered as primary, the rudiment 
of a fourth is found (cf Fig.) ; but this is further differentiated 
only in exceptional cases. We thus have at least four ethmo- 
tnrbinals represented in the developing human nose, with three 
olfactory meatuses; and this arrangement recalls those Mammals in 
which there are four corresponding ridges present in the adult. 

[Concerning variation of 
the olfactory meatuses of 
the human adult, on recent 
e\ammation of 152 indi- 
viduals,^ the dominant con- 
dition — presence of three^ 
was observed in 56 per 
cent four were noted in 
41 per cent, and five in 
1 A per cent. In three 
instances (i.e. approximately 
in 2 i-cr cent) only two were 
found the superior turbi- 
nated bone being absent; 
and m one of these " there 
Pia 88 — SiamiL Section THUoraH the ,^„„ „ u, ■ t i i i.„ c 
Naml A1.D BocciL CAV1TIB8 OF TM ^^^ ^ honzoutal platc of 
Human Head cartilage projecting into the 

/, 77. ///, the th™ olfactory ndgM,«..,froiiUl Q^sal fossa from the septum 

BiQua ; an, ., aphenoidal aiaaa ; «., opening of ^~.."x- 

Eustaobion tube ; be., entrance to the mouth ; on a level with the inferior 

ttSr*' "■■ "°" "*"" '■"' ™ turbinated bone."] 

When it is further re- 
membered that the maxillary, frontal, and sphenoidal sinuses 
(«»'., s»".. Fig. 88) are also lined by olfactory mucous membrane, 

» [M&de under tha anspices of the CoUeotivB Investigation Committee of the 
Anatomical Society of Great Britain and Ireland. See Soar. Anal, and PAys.. 




THE SENSE ORGANS 143 

and that in the sinus frontalis of the embryo (as Professor 
Killian, who has paid especial attention to this subject, has 
kindly informed me) even now ridge-like structures sometimes 
occur, reminding one in the manner of their origin of the eth- 
moidal system, it seems probable that there was once a still more 
highly specialised development of the olfactory organ. 

The above remarks apply to the olfactory region proper, i,e. 
to the ethmoidal labyrinth with its olfactory ridges. I have 
so far purposely avoided the term turbinal, and have always used 
instead the word ethmo-turbinal, or Schwalbe's term " olfactory 
ridge," in order to exclude any suggestion of parallelism with the 
" turbinal " of the lower Vertebrata. But we now come to the 
question of the persistence of the latter among the Mammalia. 
To these animals it has been handed down as the " inferior 
turbinal," but it now possesses no olfactory epithelium, having 
evidently undergone a change of function. In animals in which 
smell is acute, it is. folded or more or less branched, i.e, is much 
more complicated than in animals with less keen scent, in which 
it is merely singly or doubly scrolled. The latter must be con- 
sidered as the more primitive condition, from which the former 
was secondarily developed. 

The conditions which have led up to reduction of the olfactory 
organ in the vertebrate series are very various. In Man its 
degeneration is due to the subordinate part played by it. The 
olfactory apparatus is here, as Broca has rightly remarked, but a 
modest vassal of the brain, which does not reach the perfection 
of the other higher sense organs. 



Jacobson's Organ 

The first indications of this organ appear to occur among the 
tailed Amphibia,^ in the form of a small ventral diverticulum 
of the nasal cavity (Jc, Fig. 89, A, B), which either retains 
its original position throughout life, or in the course of develop- 
ment becomes shifted so as to lie in the maxillary sinus (Fig. 
89, E). 

At exactly the same point near the nasal septum, where, in 
the Amphibia, this organ arises, in the Amniota Jacobson's organ 
is found, in the form of a diverticulum of the principal nasal 

^ Apparent indications of this apparatus are forthcoming in certain fishes 
{Polypterus), 



THE STEUCTUBE OF MAN 




THE SENSE ORGANS 




Fio. 89. — A-D, Various Staoes opDbvelofiiehtc»'[the bo- called] Jacobsom'b Orqam 
or THE UflODELli, illustrated by a, oeries of transTerae Bectious. F, transversB 
section through the nose and Jacobson's organ of Lacerta agUU ; O, the same of 
a placental Mammal ; H, the esoie of (ymitiuahyruivaa, after Symington ; I, diagram- 
matic side view of G. 

In A the organ commences medially and hasally ; in D the lateral position is attained ; 
E. the Q^iatophvmf, in which separation from the principal cavity is effected ; na., 
nasal cavity i jc, Jacohson's orgau ; cj., Jacobaon's cartilage ; g.ia., inl*r-maiUlary 
gland ; g.n., nasal gland ; n.o., olfactory nerve ; it-t., trigeminal nerve ; d.n., nasal 
duct ; RUr., upper jaw ; sp., septum nasi ; o.d^ dumb-bell-shaped bone, forming a 
support for Jacobson's organ. 

cavity {jc. Fig. 88, G, H, I). In most Mammals this becomes 
couatricted off and secondarily connected with the buccal cavity. 
A lateral displacement does not take place, and the organ remains 
between the floor of the nasal cavity and the roof of the mouth, 
i.e. in its original position. It is always lined with a pronounced 
sensory epithelium, innervated by the ventral fasciculus of the 
olfactory nerve {n.o., Fig. I). 

Eecent investigation has proved, without doubt, that vestiges 
of a Jacobson's organ are to be fotmd in adult human beings. 
Before considering these in detail, however, certain structures 
which attracted the attention of the earlier investigators need 
to be dealt with. 

Huscke's " plough-share cartilage " in Man was formerly 
regarded as the vestige of the two cartilaginous tubes lying near 
the base of the nasal septum, which in many lower Mammals 
envelop the organ of Jacobson. This is incorrect, since, as 
Spurgat baa shown, the same cartilages are found in the human 
organs of Jacobson as in those of the lower Mammalia, but in a 
much reduced condition. These organs, together with the Sten- 
son's canals, open into the buccal cavity through the ductus 



146 THE STRUCTURE OF MAN 

incisivi. The latter are sometimes wide, sometimes constricted, 
and they commmiicate with the mouth either independently or 
by a common orifice. In fresh embryos the passage of the canal 
is to be found open only in exceptional cases ; there are usually 
two canals present on both the buccal and nasal surfaces of the 
palate, the former of these are usually the more prolonged. Both 
pairs are lined with mucous membrane, and, ending blindly, form 
together an obtuse angle. Traces of the buccal ends of these canals 
may still be found in some adults in the form of epithelial 
strands ; as a rule, however, they disappear without leaving any 
trace, while the upper or nasal portions persist. 

Between the two canals, or their vestiges, which run up from 
the buccal cavity just behind the inner incisors, there is on the 
palate a papilla, the so-called papilla palatina incisiva {jp.p.. 
Fig. 95). This has been investigated by Merkel, and found to 
be a sensory organ, but its physiological significance is not under- 
stood. 

Eeturning to the actual organ of Jacobson in Man, the 
epithelial tubes which form its inner lining agree in every 
respect morphologically with those of certain lower Mammals 
{e.g. the Eat). The epithelium of the outer wall somewhat 
resembles that of the regio respiratoria of the nasal cavity, and 
that of the inner wall, which is almost four times as thick, that 
of its regio olfactoria. There are no traces, however, of the 
characteristic filamentous olfactory sense -cells — the cells being 
much more like the supporting cells of the olfactory epithelium. 
Between them occur short fusiform elements which do not reach 
the surface (and may perhaps be incompletely developed olfactory 
cells). Numerous acinose glands open into the organ. 

Although no nerves have been as yet discovered in the organ 
in the human adult, in the embryo, as in the lower Mammals, 
a well-defined branch of the olfactory nerve {n.o., Fig. 89, 1) runs 
to it. 

All things considered, the organ of Jacobson in Man has 
certainly all the characteristics of a vestigial structure. This is 
seen not only in its inconstant occurrence, in its frequent one- 
sided development, and in its degeneration, which commences 
even during foetal life, but in its histological structure (Merkel, 
Schwink, Chiarugi). In Anthropoids it is still further reduced. 

[This organ attains its fullest morphological development 
in the Monotremes (Ornithorhyiichus) (Symington).] 



the sense organs 147 

The Projectile Kose 
Whereas the oIfaj:tory ridgea and Jacobson's organ of Man 
are to be considered degenerate, the projectile nose and its 
skeletogenous supports are in a progressive condition ; they may 
indeed be considered as specifically human structures. It cannot 
as yet be said with certainty what gave the first impulse to their 




Fio. (to. — Heads of two Huhan Embhios. 
at tlie end of the second ; B, at the beginniDg of the tljird mouth (after W. His}. 
av., eitemal auditory involution, with the pinna {p.) seeu developing ftround it, v., 



development, 
inquiry.^ 



This question awaits an extended morpholt^ical 



The Eye 



The human eye itself shows few vestigial structures ; and 
these, being limited to the embryo, are but transitory. I refer 
to the arteria hyaloidea which passes through the vitreous body 
within Cloquet's canal, and which is closely related to the fcetal 
choroidal fissure. The former plays an important part in the 
nutrition of the central part of the eye during embryonic life. 
This is provided for in Fishes and Keptilea by organs known aa 

' This baa been UDdertakea bj my pupil F. Spurgat, and a preliminary report on 
his first series of oburvations will be found in the Anal. AiKxiger, Bd. viii. p. 228. 



148 THE STRUCTURE OF MAN 

the processus faleiformis and the pecten which are permanently 
retained, but in Man the corresponding structure undergoes com- 
plete degeneration before birth. 

We meet with indications of atavism in connection with the 
accessory parts of the eye. In the fissura orbitalis inferior, for 
instance, there is an accumulation of smooth muscle, which is 
the last vestige of the well-developed musculus orbitalis of lower 
Mammals. In these animals the orbital fossa is usually in open 
communication with the temporal, i.e. the two are not separated 
by a bony septum (cf. ante, p. 58). This aheet-iike muscle 
forms the boundary between the temporal and the orbital fossae ; 
it is innervated by nerves arising from the sphenopalatine 
ganglion, and contracting, under their action, causes the eye to 
protrude.' 

The occasional presence of laterally and medially diverted 
oH'shoots of the levator palpebrte superioris muscle suggests that 
it may once have been njtore extensive, than at present. It may 
be regarded as the vestige of "the much fliore strongly developed 
palpebralis muscle of certain lower Mammals ; further investiga- 
tion of this subject howe\ei is required. 

Great interest attaches to the fold of the conjunctiva which 
lies at the median angle of the 
eye, and is known as the plica 
semilunaris (pi.. Fig. 91). Thia 
corresponds with the third eye- 
lid, the so - called nictitating 
membrane, of the lower animals. 
In Birds, Anurous Amphibians 
[some Sharks], and in many 
' p/ Eeptiles it is highly developed, 

Fjo. 91.— Hdhan Eyk. and, by means of a special mus- 

c.;.,caniiicuuuciir>-in»iia;pi piio« ^^^^^ apparatus. Can be drawn 

semilunaria (vestigiBl third eyelid). rf ' " 

across the eyeball. It serves not 
only to cover, but to keep clean the surface of the eye, the 
upper lid [which in Man performs that function] being im- 
movable, and the lower slightly movable or but little developed. 
In Man, as in the Apes, in association with the absence of a 
retractor bulbi muscle, this third eyelid has undergone great 
degeneration, but it may still enclose (more frequently in Negroes 
than in Caucasians) a cartilaginous support. Among sixteen 

* Nussbaum lias recently announced the discovery in a, human orbit of a muscle 
homologous with the retractor bulhi of loner vertebrata. This awaits confirmation. 




THE SENSE ORGANS 



149 



pure Negroes this cartilage was found by Giacomini in twelve 
individuals. 

The plica semilunaris varies greatly in size at different ages 
and in different races. In the new-born child, and during the 
early years of life, it is broader than later, when it does not exceed 
IJ to 2 mm. in breadth. One known exception to this rule is, 
however, found in the Malay tribe of the Orang-Sakai, in which it 
reaches a breadth of 5 to 5 J mm. It would be worth while to 
examine other tribes in this respect. 

In the caruncula lachrymalis (c.L, Fig. 91), which lies near the 
plica semilunaris, glands are to be found, which in their structure 




FiQ. 92. — Diagram to illustrate the Shifting of the Lachrymal Gland, 

WHICH HAS TAKEN PLACE IN THE COURSE OF PhLYOGENY. 

The gland shifts in the direction of the arrows ; a, its position in the Amphibian ; ft, in 
Reptiles and Birds, and in certain human beings, in which case it may be regarded 
as atavistic ; c, normal position in Man. 

greatly resemble the lachrymal glands. These " nictitating glands " 
constitute a distinct series and are in no way connected with the 
sweat and MoUerian glands (Peters). Further, sebaceous glands 
and fine hairs are, in the Primates, found near the caruncula. 

Finally, a mention may be made of accessory lachrymal glands 
which, with their ducts, occasionally lie near the conjunctival sac 
at the lateral angle of the eye (cf Fig. 92) — i.e. in a position 
approximate to that of the lachrymal glands of Amphibia and 
Eeptiles, and indicative of a gradual shifting of the lachrymal 
apparatus in the course of Phylogeny. 

Long stiff hairs which occasionally appear in the median 







/' 



160 THE STRUCTURE OF MAN 

region of the hiiman eyebrow recall from their position the 
feelers [or supra-orbital vibrissse] of the lower Mammala They 
have been already dealt with {ante, p. 4). 

A well-marked variation of the upper eyelid, apparently due 

to arrested development during foetal 

life, is that resulting in the formation 

ep. ^^i#^^^^^^ of the so-called epicanthus («^., Fig. 

93). This, as its name suggests, is a 
prolongation of the lid, which extends 
more especially over the inner angle 
of the eye. In certain races, such €U3 
the Mongolian, this variation is con- 
spicuous, giving rise to the slit -like 
appearance and oblique position of the 
aperture of the eye. The obliquity, 
however, is only apparent, for it 

Fig. 93.— Eye op a Mongouan, vanishes if the skin above the nose 
WITH THB Epicanthus (ep.)- be tightly stretched. The epicanthus, 

(After Merkel.) .^ • .1 -r 1.1. 

as it appears m the Japanese, has been 
very exactly described by Balz, who points out that it results 
from the flatness of the bridge of the nose — the superfluous skin 
forming the fold in question. It is a matter of interest that a 
similar condition has been observed among Caucasian children. 
According to Eanke, about 6 per cent of these exhibit a markedly 
Mongolian type of eye during the first six months of their lives. 



The Auditory Organ 

In describing the skeleton of the head, mention has been made 
(ante, p. 49) of the post-oral branchial sacs which characterise 
a certain embryonic stage, and of the auditory ossicles (p. 64). 

The latter arise partly from the original suspensory apparatus 
of the lower jaw, i,e, from the visceral skeleton. As to the 
former, only the anterior sac persists in Mammals ; and from 
this (the spiraculum ^ of the lower Fishes) the cavity of the middle 
ear (Eustachian tube and tympanic cavity) develops. 

^ [Considerable interest attaches to the fact that the only living Vertebrates in 
which this, the " hyo-branchial cleft " of comparative embryologists, is absent, are the 
Marsipobranchii (Lampreys and Hftgs) and the Teleostean or Bony Fishes. Its occur- 
rence in the embryos of the former group is now well known (Shipley, Q%. Jour. Micr, 
Sci.^ vol. xxvii. p. 349), and Sagemehl has described its apparent vestige in certain 
adult members of the latter {Morpholog, Jahrh,, Bd. ix. p. 213). It is, however, in- 
sufficiently recognised that the painstaking researches of Ramsay Wright have 



THE SENSE ORGANS 



We have thus, in each case, a typical example of change of 
function. 




FlO. 94.— DUOBAa TO ILLnSTHiTK THE MeTAMOKPHOSIS DDBIIia DBVBLOPMEHT OF 

(I-V) THE First to tub Fiftb Viscbbal Skeletal ARCKga. 

From the firat arch (the so-called Meckel's cartilage) two of the auditor; ossicles, the 
iniUleuH gjid the iucus (mi. and in.), are represetited as arisiug proiimally, but about 
this there is still considerable doubt (cf. anle, p. 64). p., pinua ; il., stapes ; j/r., 
processus muttoldeus of skull. 

From the seeond (hyoid) aich arise, pronimally, the processus styloideua (p.».), 
distally the anterior or lesser comua of the hyoid {c.n.), and a portion of the baai- 
liyoid or copula (bi.). By far the greater portion of this arch becomes the stylo- 
hyoid liganieut (tg.). It is very doubtful whether tlie arch of the stapes also arises 
from tlie proximal portion of the second arch ; the basal plate of the stapes, at any 
rate, appears to arise iudepeudently of it. 

The third arch gives rise to the greater part of the body (is.), aud the poslsrior 
or greater horn, of the hyoid (c.p.). 

The fourth arcli gives rise to the upper segment (Ik'.) of the thyroid cartilage 
and tlie fifth lo the lower oue (th'.). The aryteuoid cartilage (a.r.) is probably a deri- 
vative of t)ie fifth arcli. ic, the cartilsgo triticea ; a:, cricoid cartUago; tr., trachea. 



|>rovcd its regular occurrence, in a modified form, tliroughout the living Ganoids ; 
and furtber, that in these fialiea aud certain Selachians it gives off a diverticulum 
(the canalis tnbo-tympanicus). which there is reason to regard as the possible homo- 
logue of the middle auditory chamber of the terrestrial Vertebrata (cf, Ramsay 
Wright, Jour. Anal, and Phys., vol. lix, p. 476),] 



152 THE STRUCTURE OF MAN 

The pinna of the ear deserves special attention. In recent 
years it has been thoroughly investigated by Schwalbe, the results 
of whose researches are here incorporated. This pinna (p., Fig. 90) 
is so elaborately modelled a structure that we can hardly imagine 
it to be degenerate. It undergoes marked variation and adapta- 
tion in different races, tribes, and individuals, as well aa at 
different ages. On close examination, variation is found, for the 
most part, to affect those portions of it which stand out freely 
from the head in a postero-dorsal direction. Schwalbe calls these 
parts the " ear-folds," distinguishing the basal region as the zone 
of the auditory prominence (cf. Fig. 71). 

The pinna of Man arises from six prominences which develop 
near the anterior visceral cleft (au,, Fig. 90), and are called the 
branchial auricular prominences. In the adult pinna they are 
still evident as the helix, crus antihelicis inferius, crus helicis, 
tragus, and anti tragus (cf. Fig. 71). The human pinna, as 
compared with that of Apes, would appear to be a degenerate 
structure ; and in reality it is much reduced, being rolled over 
in such a way as greatly to modify the upper edge of the helix 
and part of the antihelix. 

The variations of the ear -folds are of great interest, and 
deserve close attention, in connection with the primitive history 
of Man. 

When we examine the highly movable ear of the Ungnlata, 
we find that the ear-fold gives rise to a very efficient sensitive 
auditory funnel, which lies parallel to the axis ^ of the ear, and 
ends in a free tip (spina). 

In the Primates the pinna is much shortened, and is thrown 
into folds (helix and antihelix) running at right angles to the 
axis of the ear. Schwalbe finds two forms of free tip in the 
Apes. (1) The Macacus or Inuus type (Fig. 71, C); and (2) the 
Cercopithecus type (Fig. 71, D). In the former (C), which some- 
what resembles in shape the ear-fold in human embryos at from 
the fourth to the sixth month, there is a freely developed edge of 
the helix which is not rolled over, and a distinct tip, always in 
the same place. 

From the eighth month, the human ear-fold enters upon a 
degenerative process, which essentially consists in the roiling 

^ By the axis of the piiina (regarded as a standard of measurement) is meant 
a line which connects the true tip of the ear (Woolner's and Darwin's tip [spina]) 
with the incisura auris anterior (cf. s.\s.",s."\ Fig. 71, B). By the breadth of the 
organ, in both Man and the lower mammals, is understood the measurement of the 
attached portion (base of the ear). 



THE SENSE ORGANS 163 

over of the edge of the ear, and in the greater development of 
the antihelix. The tip, at the same time, shifts down along the 
posterior edge of the helix, without, however, becoming rolled in ; 
and there thus arises the so-called Cercopithecus form (c£ Fig. 71, 
D) of the human embryo. 

If the rolling in of the tip takes place, we have a third type 
of ear, in which the tip is turned forwards (Darwin's tipped 
ear). This (Fig. 71, E) is the usual condition of the human 
adult, but many modifications of it are realised, the tip some- 
times entirely disappearing as a free projection.^ 

Besides the degeneration which finds its expression in the 
reduction of the human ear-fold or pinna,^ its cartilage is also 
degenerating. The external auditory passage is among the lower 
Mammalia (Marsupials) beset by three separate cartilages, movable 
upon each other. The auditory canal of the child still distinctly 
reveals this structure, although the alleged complete independence 
of the basal piece affirmed by Biirkner has not been fully estab- 
lished (Schwalbe). The original clefts between the cartilages are 
incompletely retained as the incisurse Santorini. 

Secondly, the cartilaginous spina helicis (processus spinosus 
helicis) is completely fused with the other cartilages of the pinna. 
It corresponds in position with the free tip of the organ, and is 
the homologue of a cartilage which, in many Mammals (Ungulata, 
Carnivora, Eodentia), is independent, and is known as the scutulum 
(clypeus or rotula). This scutulum fuses with the principal cartilage 
of the ear in the Lemuroidea and the Apes, as well as in Man.^ 

^ One curious variation is the occurrence on only one side of Darwin's process. 
In a batch of military recruits it was found to be of medium size on the right side in 
330 men, and on the left only in seventy-nine, and was thus four times as frequent on 
the former as on the latter. It was found to be remarkably large on the right side 
in ten individuals, and on the left only in one (Ammon). 

2 The ear-fold may undergo reduction in Mammals which live underground or 
in water. The rudiment of a pinna has been found in the embryos of some Whales 
[and a structure which has been similarly interpreted may occasionally appear in the 
adult Cetacean]. According to this, the ancestors of existing Whales must have 
possessed an external ear, and since such an organ would occur in land animals, 
we find in this fact a proof of the descent of the Whales from terrestrial Placentalia 
(Kiikenthal). 

^ In rare cases the scutulum may remain separate, even in Man. The familiar 
lobulns auriculae, a non- cartilaginous fatty tegumental fold, first occurs in the 
Anthropoids. In Man it undergoes many variations of form and size, and is not 
infrequently entirely absent. It is never found in people of genuine Kyban descent, 
nor in the Cagots of the Pyrenees (Blanchard). 

I have to thank Herr Otto Ammon of Carlsruhe for the following statistics 
obtained by him in connection with the militaiy recruiting in Baden for 1889 : — 

In 4171 ears (of 2086 men) in the military district of Mosbach, the free lobe was 



154 THE STRUCTURE OF MAN 

We have every reason for believing that the ancestor of Man 
could move his pinna to a far greater extent than can his descend- 
ant of to-day. The pinna, no doubt, formerly took a great 
part in the play of the features, and served, as it now undoubtedly 
does in the lower Mammals, as an excellent instrument for 
appreciating the direction of sound. 

We are justified in this assumption, or rather affirmation, 
by two facts: (1) the position in which the pinna is still often 
found with relation to the head ; and (2) the presence of an exten- 
sive musculature, the primitive history of which has already been 
given, in describing the platysma myoides (cf ante, p. 105). 

With regard to the first point, it is well known that in by 
far the greater number of individuals the pinna of the ear lies 
more or less closely applied to the temporal surface of the head. 
When attention has to be concentrated in a special direction, a 
person may be seen to correct this physiologically bad arrange- 
ment by applying the hollow of the hand to the back of the 
ear, and so forming an artificial funnel like an ear trumpet. 

This proceeding is less necessary in individuals whose 
ears stand out, wing-like, from the head, i.e. are physiologically 
more correctly disposed. From the modern aesthetic stand- 
point this is a questionable advantage; but it is a peculiarity 
which has a great tendency to be handed on by inheritance. 
In any case, this position is the original one, and the flattened 
condition must be considered as secondarily acquired. 

It is difficult to decide what influences brought about the 
loss of physiological efficiency of the pinna. It may have been 
due to a gradual alteration of the resting attitude of Man ; and 
it should be generally known that deformation of the pinna, 
which often lasts for years, may be produced in children by the 
same cause. 

wanting 1511 times, i.e. in 36 per cent. It was present in 2461 ears, i.e. in 64 per 
cent ; of the median size in 2318, and specially large in 143, i.e. in 3 to 4 per cent. 
Darwin's point was not to be fonnd in 3106 cases, i.e. in 74 per cent ; it was present 
in 1066 cases, i,c. in 26 per cent ; in 1027 it was of median size, and in only thirty- 
nine {i.e. in 9 per cent) unusually large. 



THE ALIMENTARY CANAL AND ITS APPENDAGES 

Palatal Ridges 

The raucous membrane of the roof of the raouth ia thrown into. 
a more or less marked median ridge— the raphe, and into a 
varying number of paired transverse ridges (r.'p.. Fig. 95), which 
are especially well developed an- 
teriorly near the inciaora, but pos- 
teriorly become flattened out. There 
are five to aeven of these transverse 
l>alatal ridges on each side, and they 
are more developed in the embryo 
and the new-born child than in later . 
life, when their primarily regular 
arrangement disappears. Those 
farthest back degenerat-e, but the f:g. 95.— Palatk op a human 
anterior ones increase in size and bhyo at the eighth month. 

T.p., palatal nilgea ; p.p., papilla pala- 
Shltt nearer to one another as age tina; oi., the later formed alveolar 

advances. In very aged persons bonier. 

the whole system of ridges may almost, or even altogether, 




la these ridges which, as has been seen, vary to a great extent, 
we have the representatives of a larger and more numerous series 
met with in many lower Maramab (cf. Fig. 96) (in Apea there 
are as many as ten). They are, as a rule, covered with a tough 
stratified epithelium, and are functional in helping to tritiD:ate 
;tnd crush the food taken into the mouth (Gegenbaur). 

Some years ago I called attention to the fact that in the 
embryo Cat these ridges develop as rows of papillte, which later 
unite, and I put forward the suggestion that we may be her© 
dealing with the remains of palatal teeth handed down even to 
Man. Closer investigation must show whether these papillse are 
actual vestiges of tooth structures or only horny growths, such 



THE STRUCTURE OF MAN 



618 are still found among the lower Mammals in the form of 

horny teeth or ridges {Ornithorhynchus, certain Marsupials, and 




The extreme anterior border of the palate bears a median 
eminence, the papilla palatina {p.p.. 
Figs. 95, 96). On either side of 
this and of the raphe the naso- 
palatine canal, already described 
{ante, p. 146), opens. 

Teeth ^ 

The teeth are among the most 
important and the moat variable 
organs of the vertebrate body. Long 
before the appearance of the osseous 
skeleton — i.e. among the lowest Ver- 
tebrates — teeth and tooth-like tegu- 
mental scutes are found. We cannot 
be far wrong in asserting that the 
acquisition of teeth by the Vertebrata 
was a most important factor in the 
struggle for existence. The size 
and form of the teeth are greatly 
determined by adaptation to the various conditions of life. 
It is therefore often difficult to decide whether similar tooth 
forms in fossil animals are cases of analogy or of homology. It 
is quite possible for different races of animals, in adaptation to 
similar modes of life, independently to acquire a similar dentition 
[as for example in the case of the Crocodilian (Gavialis) and the 
Dolphin (Platanista) living side by side in the Ganges} If, 
among the lower Vertebrata, we set aside dental ridges resulting 
from the fusion of several distinct teeth, and the compound teeth 
of many Fish, the teeth, as far up as the lower Reptiles, are, for 
the most part, simple pointed cones. In these animals they serve 
only for seizing the prey, the further disintegration of which 
takes place tn the stomach and intestine. In the Mammalia 
the food is more or less triturated in the mouth, and that chiefly 
by the cheek teeth. 

The dentition of the Primates is, as compared with that of 

' In this account of the teeth the reeesruhes of Riise huvc been largely 



Fio. 98. — Palatal Foldb ov ti 

BiCOOl" (Procn/on lotor). 

T.p., palatal folds ; p.p., papilli 



THE ALIMENTARY CANAL AND ITS APPENDAGES 167 

Mammals generally, but little specialised. The molars in parti- 
cular are comparatively simple cuspidate teeth, such as are found 
among the oldest Mammals. Judged from the form of their 
teeth, the Primates would appear to have branched off very 
early from the common Mammalian stem. If we can draw 
conclusions from the fossils as yet found, the Apes were not very 
widely distributed in earlier periods. They probably lived, as 
they now do, as climbing animals in tropical climates. In con- 
sequence partly of their frugivorous manner of life, and partly of 
the higher development of their intelligence, their teeth, of no 
great service for warfare in the struggle for existence, appear to 
have remained comparatively simple. 

The dentition of Man agrees with that of the Old World 
Apes in number and shape of the teeth. The dental formula is : 

2. 1. 2. 3 
^•7rc.j-p.m.— m.— = 32. The New World Apes, on the other 

Z. 1. Z. o 

hand, have one more premolar in each set, their formula being 

2. 1. 3. 3 

= 36. If the teeth of Man are compared with those of 

Z, 1. o. o 

the nearly related Anthropoids, it is found that their respective 
milk teeth agree in form and size more nearly than do their 
permanent or successional dentitions. In the Anthropoids [with 
the exception of the Gibbon {Hylohates)'] the teeth of the second 
series are larger and stronger than in Man, the contrast being 
most marked in the size of the canines. The latter serve, in the 
Ape, as powerful weapons in the struggle for existence,^ and the 
premolars of the Apes are also, in consequence of the greater 
development of their outer cusps, more caniniform than in Man. 
The molars, on the contrary, are remarkably similar throughout, 
although they are larger in Anthropoids than in Man ; and in 
HylohateSy both in form and size, they can hardly be distinguished 
from those of the human subject. 

[Since, among Mammals generally], the milk teeth, i.e, those 

^ We have abundant evidence that teeth were once used by Man or by his 
ancestors as weapons of defence ; traces of such a use have not altogether disappeared 
in human beings of the present day, and I cannot refrain from quoting in this connec- 
tion a comment of Darwin which occurs in liis book on the Origin of Man. 

"He who rejects with scorn the belief that the shape of his own canines, and 
tlieir occasional great development in other men, arc due to our early forefathers 
having been provided with these formidable weapons, will probably reveal by sneer- 
ing the line of his descent. For though he no longer intends, nor has the power, to 
use these teeth as weapons, he will unconsciously retract his ' snarling muscles * (thus 
named by Sir C. Bell) so as to expose them ready for action, like a dog prepared 
to fight. " 



168 



THE STRUCTURE OF MAN 



of the first series, are as a rule far less modified than the 
permanent teeth ; and since, in view of this, it is found that 
the former agree in Anthropoids and Man far more than the 
latter, we are justified in concluding that the teeth of both 
Man and the Apes point back to a common origin from some 
more or less intermediate type. The dental formida of the 
Anthropoid Apes appears to be comparatively fixed ; but the 




.—Human Mouth, in which thk Development of the Upper Octkb 

Incibohs has been Sdffrebsed. 
ucison ; i", outer inoisora ; p.m., first premolar of the upper jaw ; c, upper 
<s which, under the special conditions, come next iu order to the upper inner 



teeth of Man show indications of gradual reduction, especially 
in the variations in the size of the molars and of the upper outer 
incisors. 

The upper outer incisor shows every transition form between 
a well -developed typical tooth and a short conical stump. In 
many individuals, however, this tooth is altogether wanting (c£ 
Fig. 97), and this dental variation may be hereditarily trans- 
mitted through several generations. 

The recent researches of Kose have revealed reason for 
believing that the upper molars of Man have been derived from 
a four-cusped tooth type, and the lower from a five-cusped type, 
and that the numerical reduction of these cusps has been due to 



THE ALIMENTARY CANAL AND ITS APPENDAGES 159 

Man's adoption of a more delicate diet, those degenerating first 
which were the last to be added to form the compound tooth, 
In the upper jaw this is the posterior lingual and in the 
lower the posterior unpaired cusp. In the third molar, the 
so-called wisdom tooth, the process of reduction may go so far 
that finally, instead of a tooth with four or five cusps, a vestigial 
stump alone appears. In a relatively large number of cases, 
indeed, no wisdom tooth at all appears, it being either not 
formed, or, if formed, retained within the gum. 

Kepeated investigations on this subject . have all tended to 
show that these signs of degeneration, so marked in Europeans, 
are found in non-Europeans also, but not at all to the same 
extent as among the Aryan race. Qtiite apart from patho- 
logical cases, upper molars with three cusps, lower molars with 
four, and reduced wisdom teeth, occur more frequently in 
Europeans than in Negroes, Mongolians, or native Australians. 
The low race last named, in its dental formula, appears least 
removed from the hypothetical original type ; for in it are still 
found complete rows of splendid teeth with powerfully developed 
canines and molars, the latter being either uniform, or even 
increasing, in size, as we proceed backwards, in such a way 
that the wisdom tooth is the largest of the series. This is 
decidedly a pithecoid character, which is always found in Apes. 
The upper incisors of the Malay, apart from their prognathous 
disposition, have occasionally a distinctly pithecoid form, their 
anterior surface being convex, and their lingual surface slightly 
concave. The ancestors of the Europeans seem to have. had the 
same form of teeth, for the oldest existing fragments of skulls 
from the Mammoth age {e.g. the jaws from la Naulette and 
Schipka) reveal tooth forms which must be classed with those 
of the lowest races of to-day. 

Apart from those variations in the human dentition, which 
tend to approximate it to that of Anthropoids, still more 
startling ones are occasionally found. For example, the 
appearance of a third premolar is not very rare. In the Freiburg 
anatomical museum there is an upper jaw with three well- 
developed premolars on each side, thus showing the dental 
formula of the New World Apes. An increase in the number of 
molars is also not very rare in both Man and the Anthropoids. 
A fourth molar, in a more or less perfect form, is to be met with 
in every large collection of skulls. Zuckerkandl has shown that 
the epithelial germ of a fourth molar is not infrequently present 



160 THE STRUCTUKE OF MAN 

in Man, and Eose has since proved that this vestige is on each 
side coincident with the end of the epithelial dental ridge. 

Bj milk teeth are usually understood the first formed 
generation of teeth. Rose, however, has recently attempted to 
show that the milk teeth do not correspond with the first series 
of teeth of the lower Vertebrates, and that they cannot be 
homologised with any one special series in Eeptiles and allied 
forms. MUk teeth, according to him, must rather be considered 
to have arisen by the concrescence of several consecutive 
generations of teeth of our ancestors, into one single, more solidly 
constructed, series, the sum of all the remaining rows which were 
once present having been in Man, as in all diphyodont Mam- 
mals, compressed into the second or permanent series. [This 
is, however, but one of several views put forward during recent 
years on the subject of the Mammalian tooth genesis. Much 
more important is the fact that, in Man, while the premolars 
are comparatively simple teeth, the milk molars which precede 
them are more complex, and more conformable, in the characters 
of their fangs and crowns, to the type of the true molars. 
These facts suggest that the deciduous (milk) molars are of a 
more primitive {i.e. a less reduced) type than the successionaL^] 

Until quite recently, the possibility of Man's developing a 
third dentition was generally denied, but it is now proved that 
that may sometimes occur. Baume, Zuckerkandl, and Eose, have 
discovered a third set of enamelless tooth rudiments on the outer 
or labial surface of the jaw, [and Schwalbe has lately suggested ^ 
that they may be the vestiges of a distinct pre-milk dentition, 
of which traces have been found by Kukenthal in the Seal, by 
Nawroth in the Pig, and, in a more extensive and calcified form, 
by Leche in the Banded Ant-Eater {MyrTnecohius). Great 
interest attaches to further inquiry into these structures.] 

In Fishes, Amphibians, and some Eeptiles, the first formed 

* [A very interesting allied case is fumished by the common Dog. In the upper 
jaw of that animal, the characters of the fourth milk (deciduous) molar are almost 
exactly those of the first true molar, and the characters of the third milk molar those 
of the fourth premolar. Similarly, the second and first milk molars closely resemble 
the third and second premolars, allowance being in all cases made for mere differ- 
ence in size. Indeed, comparison of the premolars with the milk molars and, through 
these, with the first molar, reveals a marvellous series of progressive stages in 
simplification and reduction of the type of tooth represented in the adult dentition 
by the first upper molar. I am hoping shortly to have this most important matter 
fully worked out in detail. — G. B. H.] 

2 [Cf. Schwalbe, Morph. Arheiten, Bd. iii. p. 531, and Nawroth, "Zur Ontogenese 
d. Scheweinemolaren," Inaug. Dissert. Basel, Berlin, 1893.] 



THE ALIMENTARY CANAL AND ITS APPENDAGES 161 

teeth arise in relation to epithelial papillae, which project above 
the surface of the mucous membrane of the mouth. A tract of the 
epithelium of the jaw subsequently sinks down into the meso- 
dermal tissues to form the so-called dental ridge, from which the 
actual teeth then develop. The dental ridge of the higher Verte- 
brates commences to form very early, long before the first appear- 
ance of the bones. In this early formation of the dental ridge 
the phylogenetic early appearance of teeth is ontogenetically re- 
capitulated. The occurrence of freely projecting papillae prior to 
the formation of the dental ridges seems to have been lost in 
most Mammals, through abbreviation of the embryonic stages. 
Kose has, however, lately proved the existence, in Man, of 
temporary traces of papillae at a period antecedent to the sinking 
down of the dental ridge. 

The Sublingua 

Gegenbaur has devoted special attention to a system of folds 
on the under surface of the tongue (plica fimbriata), which are 
very distinctly developed in children at and soon after birth, but 
in adults are found only in various stages of reduction. 

In its general form this organ resembles the sublingua of 
the Prosimii, in which animals it attains its most independent 
development in the Slender Loris {Stenops) of Ceylon. It is in 
this creature supported by cartilaginous, fatty, and connective tissue, 
its investing epithelium being raised into papillae and showing 
a tendency to become horny. In the allied Tardus and in Lemur 
degeneration has obviously taken place ; since, in the latter, the 
cartilaginous supporting tissue has altogether disappeared and the 
organ is no longer independent, so far as its relations with 
the tongue are concerned. The sublingua would thus appear to 
have formerly possessed a well-developed supporting skeleton, 
inherited from the lower classes of animals, and we are, in fact, 
reminded of the rod-like process of the basihyal which, in Lizards 
and some Chelonians, passes so conspicuously into the base of the 
tongue. Thus considered, the sublingua may be regarded as the 
morphological equivalent of the tongue of the lower Vertebrata, 
and the actual Mammalian tongue would appear to have been 
to a certain degree acquired [within the limits of the Mammalian 
phylum]. The tongue and sublingua thus appear to be organs 
of very different phylogenetic significance, and there is some 
reason for thinking that the muscular tongue has probably 

M 



162 THE STRUCTURE OF MAN 

been developed out of the posterior part of the degenerating 
sublingua. 

The study of Ontogeny has up to the present thrown no 
light on the sublingua. 

Before quitting the tongue the papillae foliatse should be 
mentioned. These, in Mammals, take the form of localised 
systems of lamellae, situated on the postero-lateral tongue border, 
and having their epithelium thrown into a series of flask-shaped 
depressions. In Man these papillae vary much in form and size, 
and since they are occasionally represented by but mere traces 
they are evidently undergoing reduction. 



Thyroid and Thymus 

These two organs are developmentally related to the pharyn- 
geal region. 

The thyroid gland, in all Mammals in which it has been 
examined, arises from two ventral outgrowths, one of which is 
paired and the other unpaired. 

The unpaired constituent is closely connected ontogenetically 
with the tongue which, during development, bridges over the 
floor of the buccal cavity, enclosing a space, the wall of which 
becomes changed into an epithelial vesicle. This is the unpaired 
or median thyroid gland, and it for a time remains in com- 
mxmication by means of its duct (the ductus thyroglossus) with 
the posterior surface of the tongue, at its base of attachment. 
When this duct closes, its orifice may become converted into the 
so-called foramen coecum of the adult, and therefore belongs to 
the class of vestigial structures. The duct itself, as His has 
shown, may often be retained in the adult for a length of 2^ or 
more centimetres. Its existence explains the fact that the so- 
called middle lobe of the thyroid gland is occasionally prolonged 
upwards into a process, which often becomes constricted so as 
to form a series of from two to four longitudinally recurrent 
vesicles (bursae supra hyoidea and praehyoidea). 

The paired portions, or the lateral lobes, of the thyroid gland 
arise at the region of extreme posterior differentiation of the 
visceral skeleton, by constriction of the primary floor of the 
pharynx, near the laryngeal orifice. We have thus, here again, a 
structure of epithelial origin. At a later stage the lateral and 
median portions of the thyroid gland become approximated. 



THE ALIMENTARY CANAL AND ITS APPENDAGES 163 

The whole organ at first has an undoubtedly glandular 
character, but after the constriction is completed it undergoes a 
marked structural change. 

The manner in which the thyroid originates justifies us in 
classing it as a vestigial organ. In the further course of its 
development, however, it does not degenerate as might be 
imagined k 'priori; on the contrary, it develops into a large, 
highly vascular organ, which, according to recent clinical experi- 
ence, is of great service in the maintenance of both the bodily 
and mental health of its possessor. 

It would appear to play some important function in relation 
to the central nervous system, since its removal in animals is 
attended with the manifestation of an extraordinary number of 
pathological symptoms, — idiocy, muscular twitchings, tetanic, 
ataxic, apathic, clonic, and epileptic symptoms being conspicuous, 
with marked disturbances of the organs of deglutition, circulation, 
and respiration (cachexia strumipriva). It may further be noted 
that different classes of animals are differently affected by the 
destruction of this organ.^ 

This gland may be concerned either in the production of a 
secretion, or in the removal from the blood of substances which 
would be injurious to the nervous system; but nothing very 
definite is known concerning its functions. It is richly supplied 
with blood, indeed much more so than the brain itself. 

In the thyroid gland, then, we have evidence of change of 
function, and this is also the case, at least to a certain extent, 
with the thymus. In Mammals, and especially in Man, this 
gland is chiefly formed from a hollow epithelial outgrowth of the 
third branchial pouch, although the fourth, and to a certain 
extent the second also, take part in its formation. 

The thymus thus far resembles in its origin a gland ; but it 
loses this character, and a thorough histological change takes 
place in consequence of the wandering into it of lymphoid cells. 
This change renders its physiological significance still more 
difficult to explain. Towards the end of the second year the 
thymus (the greater part of which now lies behind the sternum, 
i.e. ventrad of the heart and of the roots of the larger blood- 
vessels) reaches its highest development, and after that period it, 
as a rule, imdergoes retrogressive metamorphosis; in very old 

^ It is difficult to decide whether and to what extent the frequent pathological 
affections of the thyroid gland (the formation of a "crop" with secondary disorgan- 
isation of the tissues) may or may not be referred to change of function within it. 



164 THE STRUCTURE OF MAN 

people, however, epithelial, lymphoidal, and fatty vestiges of 
it always occur. 

We cannot at present determine what was the original signi- 
ficance of the thyroid and thymus glands, and the like is true of 
an allied body, the so-called carotid-gland (glandula intercarotica), 
which is found at the bifurcation of the common carotid artery. 

[Concerning the thymus, however. Beard, working chiefly at 
the lower Fishes, in which it attains its greatest development, has 
recently been led to the brilliant suggestion ^ that it may be 
in them primarily protective of the branchial organs of respira- 
tion, by a process of phagocytosis, in a manner akin to that in 
which the tonsils and associated cytogenous tissues are protective 
of the main respiratory passages of the pulmonary organs of the 
terrestrial Vertebrata.] 

Bursa Pharyngea 

The primitive history of this organ cannot at present be 
certainly determined. In Man it appears at about the third 
month of foetal life, on the posterior pharyngeal wall, as an 
epithelial evagination, directed upwards and backwards towards 
the occipital bone. During embryonic life this structure becomes 
shifted in the course of its growth ; its canal lengthens, and 
finally approaches the tonsils ; after this it participates in all the 
changes which affect these organs. Chief among these is degenera- 
tion, which normally takes place before the time of puberty. The 
degenerative processes bring about shrinkings, fusions, the formation 
of crypts and cysts, and other modifications so diverse that hardly 
any two cases are alike, and the most different accoxmts are con- 
sequently given of them in the literature of the subject. 

The following lower Mammals are known to possess a bursa 
pharyngea; the Alpine Marmot {Arctomys marmota), the Pig 
(Sus scrofa), the Eoebuck (Capreolus), and the Bear ( Ursus). In 
no other Mammals examined has anything of the kind been 
found, and since no traces of the organ are to be observed in the 
lower Vertebrata, its primitive history and physiological signifi- 
cance remains problematical (Killian). 

(Esophagus and Stomach 

In their fully developed condition the oesophagus and 
stomach show no anatomical peculiarities which need be specially 

^ [Anat, Anzeiger, Bd. ix. p. 482.] 



THE ALIMENTARY CANAL AND ITS APPENDAGES 165 

mentioned here. Attention may, however, be drawn to the saccus 
csecus, which is, as it were, indicative of the commencement of a 
process of chambering in the stomach, the antrum pyloricum, and 
a constriction (c'., Fig. 98) which but very rarely occurs ^ near the 
middle of the pyloric region. 

The cesophageal mucous membrane, which after birth is 
covered with a dense stratified epithelium, is in the embryo 
beset by a columnar ciliated epithelium, and thus recalls very 
primitive conditions. In Amphioxus and the yoxmg Lamprey 
(Ammocoetes), for example, nearly the whole intestine is still 
lined with a similar ciliated epithelium. In the adult Lamprey 
it is somewhat more limited, and it is still to be found at various 
parts at least of the intestine, in a large number of the Anamnia. 
Ciliated epithelium is also frequent in the oesophagus of Eeptiles, 
and it has even been proved to exist in the intestinal canal of 
some Mammals, at least over small areas. 

[A similar replacement of ciliated by stratified non- ciliated epithelium 
may take place over localised areas of the mammalian trachea. In the Dog 
and Gat, for example, this change is effected over areas of attrition, resulting 
from a folding over of the tracheal wall ; and this and other allied considera- 
tions have led to the application of the term "frictional" to stratified 
squamous epithelium (cf. Haycraft and Garher, Qu. Jour. Misc, Sci., vol. xxx. 
p. 519).] 

Muscle bundles often occur between the posterior wall of the 
windpipe and the cesophagus, at the point where the left bron- 
chial tube crosses the latter, and at other parts of the intestinal 
canal, e.g. the duodenum. Their significance is imdetermined ; 
but their inconstancy, variability, and feeble development suggest 
that they may be among those organs which are being gradually 
lost by Man. 

The comparative anatomy of the stomach, and of the course 
and ultimate distribution of the vagus nerve, prove that the 
former, like some other organs of the viscera {e.g. the heart, the 
thyroid, and the thymus glands), originally lay farther forward, 
i.e. nearer the head, and that it has secondarily shifted back 
(c£ ante, p. 38 and Fig. 31). 

It not infrequently happens that a blind diverticulum 
(diverticulum ilei or diverticulum of Meckel) arises from the 

^ I noticed this constriction twice during the ordinary dissecting course in this 
University in the winter of 1892 and 1893 ; and careful dissection showed that there 
was at the constricted part a ring-like specialisation of the circular musculature. 




166 THE STRUCTURE OF MAN 

lower part of the small intestine.^ This diverticulum is connected 
during the embryonic period, and sometimes still longer, with the 
navel, by a cord, containing the last vestiges of the ductus 
omphalo-mesentericus, which connected the yolk-sac with the 

intestine. We have in this 
a mere vestige of a foetal 
organ. 

[On examination of 
769 bodies, at the insti- 
gation of the Collective 
Investigation Committee of 
the Anatomical Society of 
Great Britain and Ireland,^ 
the diverticulum ilei has 
been encountered in but 
sixteen cases, or in little 

Fig. 98. -Human Stomach. ^^^.^ ^Yism 2 per cent, 

a., oesophagus ; j?y., pylorus ; c'.c"., constrictions ^ • i • . i j.i. t_ j. 

of the pyloric chamber. Special interest attaches to 

EoUeston's report upon 
the examination of 337 individuals (nearly 44 per cent of 
the whole number) which were equally representative of the 
two sexes, as nine of the ten possessed of the diverticulum 
were males.] 

[A remarkable case has more recently been put on record by 
Buchanan,^ of an adult male subject in whom this appendage had 
a total length of 9 cm. and a basal circumference of 11 cm., 
and contained a spacious central cavity having a wide aperture of 
commxmication with the ileum. The remaining alimentary 
viscera were strikingly aberrant, the colic head and the coecum 
being directed towards the left hypogastric region (instead of the 
right), the ccecum terminatiijg in an appendix vermiformis which 
measured 13^ cm. in length.] 

^ According to Sappey, the length of the intestine in white men of middle height 
is 9600 mm., — 8000 of which are to be reckoned to the small intestine, and 1600 to 
the large one. According to the researches of Chudzinski, who examined nine 
Negroes, the total average length was 8667 mm., i.e. almost 1000 less. There were, 
however, great variations in length in different individuals. If the length of the 
intestine is affected by the height of the individual, it can hardly be so to any great 
extent. 

The fact that the total length of the intestine is less in Negroes is due to the 
comparative shortness'of the small intestine, for the large intestine is longer in the 
black than in the white races. 

^ [Jour, AnaL and Phys.y vol. xxvi. p. 91.] 

•^ [Ibid. vol. xxvii. p. 659.] 



THE ALIMENTARY CANAL AND ITS APPENDAGES 167 



The Vermiform Process 

The processus vermiformb (ap.. Fig. 99) is a feebly de- 
veloped organ which liea at the end of the short coscum (cos.), 
and possesses a considerable morphological interest. In Man its 
average length is 8^ cm., but it may be but 2 cm., or on the 
other hand, some 20 to 23 cm, long. 

Considerable variation also occurs in its width and disposition 




FlO. fla.— ThB C(BCnM AND PROCESSUS VeBMIFOBUIS 

i.l., large intestine ; i.a., Bmall intestine ; a 



{cf p. 166), and in the folds of mucous membrane which bound 
its ostium. Indeed, everything points to the retrogressive 
character of this appendage, and justifies us in concluding that 
the total length of the alimentary tract was formerly greater 
than it now is. The great variations in the form and size of 
the ccecum (c(e.) also support this view. 

According to Eibbert the processus vermifonnis at different 
ages measures as follows : — 



THE STRUCTURE OF MAN 



At birth 3| cm. 

Up to the 5th year . . . 7| „ 

From 5—10 9 „ 

From 10—20 9f „ 

From 20—30 9| „ 

From 30 — 40 8| „ 

From 40—60 &l „ 

In old people over 60 . 8j „ 

In embryos and new-born children on the one hand, and in 

adulta on the other, the vermiform process varies in length in 




Via. 100.— Tbe Ccecuu and Veruifohu Process o 
References as in Fig. 99. 



1 UUUAN EUBBTO. 



proportion to that of the rest of the intestinal canal ; and since 
it is a degenerating organ, it is not surprising to find that it is 
most strongly developed in fcetal times, and does not grow at 
a rate proportionate to advancing age. In the embryo its 
length, in proportion to that of the large intestine, is approximately 
one to ten, and in the adult one to twenty. Further light is 
thrown on these facts by Ribbert's interesting discovery of the 
frequent occlusion of the vermiform process. He found it either 
partially or totally closed in 25 per cent of the eases examined. 



THE ALIMENTARY CANAL AND ITS APPENDAGES 169 

with ajxompanying very decidedly retrogressive changes (patho- 
logical cases excluded) in the related tissues.^ 

Taking only adults into considemtion (i.e. omitting individuals under 
twenty years of age in whom variationB are comparatively rare), out of 100 
vermiform proceaaeB 33 were found partially or wholly closed. Complete 
occlusion throughout the whole organ waa found in a very small number, 
ahout 3j per cent. Partial occlusion is much more frequent, all degrees 
heing found, from the first narrowing to the complete closing of the lumen. 




In rather more than half of the cases the occlusion affected a quarter of the 
lenjjth ; in nearly half of the remainder its extent varied hetween one 
quarter and three quarters, and in only a very small number did it affect 
more than three quarter*, or close up the tube. 

This process of occlusion is equally marked in both sexes, 
and the statistics concerning its occurrence at different ages are 
very striking. They make it clear that there is marked increase 

* Actual pathological obliteration, nevertheless, occasionally occurs at the end of 
the Termiform process. 

The occlusions which result, and which are probably always due to inflammation, 
are less frequent than the typical obliteration (Ribhert). 

1 cannot again in this connection refrain from referring to the coincidence of the 
existence of vestigial organs and the tendency to disease caused by them. 



170 



THE STRUCTURE OF MAN 



in the frequency of its occurrence in advanced age, as will be 
seen from the following table : — 

From the 1st — lOth year occlusion observed in 4 per cent. 



n 
» 



lOth— 20tli 
20th— 30tli 
30tli— 40th 
40th— 50th 
50th— 60th 
60th— 70th 
70th— 80th 






11 


» 


17 


»> 


25 


» 


27 


>j 


36 


» 


53 


w 


58 


>» 



It follows from the foregoing table that in more than 50 per 
cent of people over sixty years of age there is degeneration of the 
vermiform process. In new-born children, on the other hand, 
this phenomenon has never been observed, and the yoimgest 
child in whom it has been found commencing was five years old. 
Total occlusion is ;also similarly connected with age, though not 
in nearly so marked a manner as partial closure. It has never 
been observed before the thirtieth year ; and while it was not 
found once in individuals between fifty and sixty, it was most 
frequent in those whose ages ranged from sixty to seventy. Among 
these, nine out of the twenty-one cases recorded showed complete 
occlusion ; and since besides them there were seven just on the 
point of closure, we may conclude that more than 50 per cent 
were thus aftected. 

A relation has further been proved to exist between the 
length of the appendix and its degeneration. The longest 
appendices (21 to 15 cm. long) kept their lumen throughout; 
in those 14 and 13 cm. long, commencing obliteration of the 
lumen was observed in four cases, and in those 12 and 11 cm. 
long it was not found. From this point, however, occlusion 
again increased as the length decreased. If we leave out of 
account individuals under five years of age, in whom occlusion 
has not been observed, we find that it occurs as under, viz. — 

Where the length of the appendix is 20 cm. in 34 per cent. 









9 


»» 


18 


9» 








8 


n 


32 


•• 








7 


»> 


40 


»» 








6 


»> 


30 


»» 








5 


)> 


70 


• « 








4 


n 


66 


»> 








3 


?> 


100 


)> 



Although this connection between length and frequency of 
occlusion is, as the table shows, somewhat irregular, we may at 



THE ALIMENTARY CANAL AND ITS APPENDAGES 171 

least conclude that, as a rule, the shorter appendices show 
occlusion more frequently than the longer (Eibbert). 



The Liver and the Pancreas 

These two organs, which are genetically closely related, 
occasionally show variations in the manner of their lobation which 
may amount to constriction, and in the relations of their ducts. 

[Kecent investigation at the hands of a number of independent 
workers has revealed the fact that the pancreas, in all classes of 
Vertebrates, is a compound organ, derivative of from one to four 
diverticula of the gut, and in most cases from three, as is said 
by Felix ^ to be the case in Man himself. One (or more) of 
these primitive outgrowths gives rise to the chief duct (or ducts) of 
the adult organ, the rest usually becoming obliterated with advanc- 
ing development. Pending the working out of further details, 
considerable interest attaches, to the recent discovery by KoUe- 
ston,^ that the duodenum of the human adult may sometimes 
bear a diverticulum (proved to be distinct from the "ampulla 
Vateri ") which enters the substance of the pancreas, and which 
there is reason to suspect may be a persistent vestige of one of 
the pancreatic outgrowths of the embryo.] 

The average weight of the liver is said to be 1451 grs. in 
the white races, 1266 grs. in the black. 



The Eespiratory System 

The visceral skeletal arches, which lie ventrad of the cranium 
proper and are intimately related to the cephalic portion of the 
gut, have been already mentioned in dealing with the head 
skeleton, and their great phylogenetic importance has been 
pointed out (cf. antCy pp. 49 and 64, and accompanying Figs.). 
A few additional remarks, however, are here necessary. 

Whereas certain Fishes (primitive Selachians) have from six 
to seven pairs of branchial pouches,^ Vertebrata somewhat higher 
in the scale (Turtles, Lizards, and Snakes) develop but five pairs, 

^ [Cf. Stohr, AncU, Anzieger, Bd. viii. p. 206.] 

^ [Jour. Anat. and Phys. , vol. xxviii. p. xii. ] 

' [It is insufficiently recognised that the " Hag Fishes '' may bear many more than 
this, and that in one species of these (Bdellostoma polytreina) from thirteen to four- 
teen pairs are present (cf. Giinther, Brit. Mus. Cat. of Fishes^ vol. viii. p. 612, 
and Schneider, Archivf. NatUrgesch., Bd. xlvi. p. 116.] 



172 THE STRUCTURE OF MAN 

which are destitute of branchial organs, and of these {e.g. in the 
Lizard) only the three anterior, as a rule, break through the outer 
integument. The fourth, in exceptional cases, may also break 
through, but this never occurs with the fifth. The same is the 
case in Birds, except that in them the third pair of sacs open 
externally only in exceptional cases, and that the fourth and 
fifth pairs, which are inconstant in their appearance, never break 
through. In Mammals and Man only four pairs of branchial 
sacs arise, and here also those which lie most posteriorly are 
decidedly vestigial in character. For this reduction a parallel 
is forthcoming in the branchial apparatus of the Anamnia ; 
and there is thus evidence both in Phylogeny and in Ontogeny 
of a progressive suppression of the branchial pouches and arches 
in postero-anterior succession. 

The branchial pouches and the skeletal arches which support 
them thus belong, in the higher Vertebrata and Man,^ in which 
they never bear functional respiratory organs, to the category of 
typical vestigial structures [inherited and for the most part lost 
— unintelligible, as Gegenbaur long ago insisted, except in the 
knowledge, furnished by comparative morphology, that in certain 
lower animals their full development is indispensable to exist- 
ence]. 

There occasionally occur in the anterior cervical region in 
Man " fistulee," which may penetrate a greater or lesser distance 
in from the integument, or may bound canals which even open 
into the pharynx. These are abnormal structures, due to arrested 
development, under which branchial clefts have not become com- 
pletely obliterated. In dealing with the auditory organ details 
have already been given {antey p. 150) of the relationship of 
the cavity of the middle ear (Eustachian tube) to the modified 
remnant of the first visceral cleft, which in the higher Vertebrata 
has imdergone a new development, in adaptation to a change of 
function. 

The Larynx 

The study both of the innervation of the musculature of the 
larynx, and of the genesis and Comparative Anatomy of its 
cartilaginous framework, strongly suggest its origin, for the 

^ The branchial sacs, and the external branchial furrows in the outer integument 
which correspond with them, are most distinctly visible in human embiyos of 3-4 
mm. in length. 



THE ALIMENTARY CANAL AND ITS APPENDAGES 173 

greater part, from branchial or visceral structures.^ It may be 
considered as certainly proved that the upper part of the thyroid 
cartilage arises out of the fourth and the lower out of the fifth 
primitive (i.e. the second and thii-d branchial) visceral arch, and 
it is probable that the fifth branchial arch gives rise to the 
arytenoids. 

With regard to the Mammalian epiglottis, it seems now 
tolerably certain that it does not owe its origin merely to the 
mucous membrane of the floor of the mouth, but that it repre- 
sents an originally paired skeletal element which, in the course 
of phylogeny, has passed from the condition of hyaline- to that 
of fibro-cartilage. [This view receives support from the investi- 
gations of Goppert, who has recently given reasons^ for believing 
that the cartilages of Wrisberg and the epiglottis, which are 
frequently in organic continuity among the lower Mammals, are 
specialised portions of one original structure.] Any attempt, 
however, to derive the epiglottis from the branchial skeleton 
seems, in the present state of our knowledge, beset with diffi- 
culties.^ 

[It is now demonstrated that the upward prolongation of the 
Mammalian epiglottis involves that organ in a relationship with 
the velum palatinum (furnishing a raison d'Stre for the existence 
of the latter), for the purpose of restricting the respiratory passage 
(narial pharynx). Special inquiry has also shown that in both 
the young and adults of representatives of all orders of Mammals, 
the epiglottis, when at rest, lies above the velum in an intra- 
narial position. Man is, however, an exception to this rule, at 
least in the adult state, and there is reason for believing that 
the velum and epiglottis have, in him, suffered a loss of connection 
by the specialisation of the latter more particularly for vocalisa- 
tion. It is yet uncertain whether the epiglottis of the human 
embryo does or does not occupy the intra-narial position *]. It 

^ The hyoid and the thyroid skeletal apparatus are still closely connected in Omith- 
orhynchuSf and bear distinct traces of their branchial origin, as not only lateral 
arches, but portions of their median elements or copula can clearly be recognised. 
In the higher Mammalia the hyoid separates from the thyroid, although the 
two continue to be related (cf. the cartilago triticea, arUe^ Fig. 94). In Mammals 
above the Monotremata the thyroid cartilage appears to consist of a single plate ; 
but it gives some indications of its primary origin from two consecutive branchial 
arches which still remain distinct in the Monotremata (Gegenbaur). 

2 [Morph, Jahrh.f Bd. xxi. p. 68.] 

3 [Gegenbaur has recently come to the conclusion that the epiglottis is a 
derivative of the fourth pair of branchial arches, Die Epiglottis^ Leipzig, 1892.] 

■* [Cf. Howes, Jour. AncU. and Phys., vol. xxiii. p. 594.] 



174 



THE STRUCTURE OF MAN 



would, therefore, be very interesting to follow closely, in Man's 
development, the changes of position and inter-relationship 
between the larynx and the upper part of the pharynx (choanse). 
I am indebted to my colleague, Professor Killian, for knowledge 
of the fact that the larynx of the bunt?.n embryo may occupy 
a high position, the upper edge of the epiglottis reaching even to 
the uvula. 

The musculature of the human larynx appears to a great 
extent to have been derived from the 
simple sphincter and dilator appa- 
ratus of lower Vertebrata, of Lizard- 
like type. Under the more subtle 
differentiation of the laryngeal 
skeleton in Man, the musculature 
has also undei^ne corresponding 
changes — for example, there is no 
longer one single muscle for con- 
stricting the glottis, but a whole 
sjstem of such muscles. In other 
words the reptile - like sphincter 
laryngis has gained new points of 
origin and insertion in the cartilage; 
and Fiirbinger has proved that 
while this is especially the case 
■ with the deeper layers of the 
' sphincter, the superficial do not 
undergo any such marked diflfer- 
eutiation, but retain to a greater extent the original condition. 
It is in these superficial tracts that the greater number of 
variations are to be found. 

The close connection between the laryngeal and the pharyn- 
geal musculature is evidenced not only by their common relation- 
ships to the vagus nerve, but by the frequent occurrence of fibres 
connecting the crico - thyroideus muscle with the constrictor 
pharyngis inferior. 

Between the true and false vocal cords there arises on each 
side of the larynx a diverticulum known as the ventriculus or 
sinus of Morgagni (sn.. Fig. 102). This evagination is directed 
outwards and somewhat forwards ; it also projects upwards more 
or less, and may even in rare instances reach the upper edge of 
the thyroid cartilage. 

These Morgagni's pouches are susceptible of marked vana- 




Fio 102. — Human Laeybs a 
Frontal Sbchok 
Ift., thyroid cartilage , cc, cncoid ca 
tilage ; ic, first tracheal cartilage ; 
an., dnua of Morgagni. 



THE ALIMENTARY CANAL AND ITS APPENDAGES 175 

tion, and we have little difficulty in recognising in them the 
homologues of the "vocal sacs" of the Monkeys. The latter 
can be filled with air from the larynx, and in certain Anthropoids 
they may extend far down in the neck, or even to the shoulder 
or thorax. These sacs, which, when distended, are reaUy 
immense, may be partly enclosed in an osseus capsule produced 
by the transformation of the hjoid .(Mycetes). It seems to me 
that they may not only act as resonators when the animal howls, 
but that, when inflated, they may serve to intimidate enemies. 

Gruber [and Rudinger] have described cases, in Man, in which the sacs 
broke through the thyroid membrane and came to he, hke those of the Apes, 
outside the larynx. [In one case of Rudinger's the sac of the right side 
was alone present The same variation has been observed by BischoflP in 
the Gorilla ; and it is interesting to note that inequality in growth of the 
two sacs has been recorded in the Chimpanzee, the Orang, and in Man.^] 

On examination of the larynxes of a nimiber of Negroes, 
Giacomini asserts that the ventriculus in no way differs from 
that of Europeans. [This is, however, in strange contradiction 
to the conclusions of Gibb,^ that the larynx of the Negro differs 
from that of the white races in the invariable presence of the 
cartilages of Wrisberg, the obliquity of the true vocal cords, and 
the pendent condition of the ventricles, which latter, according 
to him, are situated below the plane of the true vocal cords, 
instead of above it as in the whites.] 

Myologically, Giacomini's inquiry is veiry interesting. The Italian 
investigator also examined the Anthropoids, and found that while the 
Chimpanzee's larynx most nearly resembles that of Man, the Orang's is the 
least akin to it, and that of Macacus and Cercopithecits occupies an inter- 
mediate position. 

Lungs 

Aeby, from a careful study of the structure of the lungs and 
of the arrangement of the pulmonary vessels, has concluded that 
in Man the upper lobe of the left lung is homologous with the 
middle lobe of the right, and that the upper lobe of the right 
has no counterpart on the left side. The question therefore arises 
whether this asymmetry is a primitive condition, or whether the 
left lung may not once have possessed a counterpart to the extra 
lobe now borne by the right, i.e. whether the original plan of 
the tractus respiratorius, as judged by the subdivision of the 
trachea, may not have been strictly symmetrical ? This would 

* [Cf. Ehlers, Ahhandlg. K. Oesellsch. d, Wiss. GUttingerif Bd. xxviii. p. 48.] 
'^ [Mem. Anthropolg. Soc.t Lond., vol. ii. p. 1.] 



176 THE STRUCTURE OF MAN 

appear at first sight the more likely, from the fact that whereas 
in man an eparterial bronchus is present only on the right side, 
in some Mammals it occurs (either bronchial or tracheal in 
origin) on both right and left.^ 

But all these animals, as Gregenbaur has remarked, in the 
rest of their organisation do not by any means show primitive 
conditions which can be considered to bear on the genealogy of 
Man ; and great care is therefore necessary in dealing with the 
question in hand. Cases, in Man, like those described by Dalla 
Kosa and Bohls, in which an eparterial bronchus is present on 
both sides ^ must not therefore be hastily classed as atavistic. 

It is, further, a very remarkable fact that the Marsupials, 
Kodents, Insectivora, Lemuroidea, and Apes, show no sign of 
original bilateral symmetry of the lungs. Further, the ontogeny 
of Man throws no light on the subject. We therefore at present 
can neither decide along what line of descent the Mammals 
above referred to may have inherited their symmetrical eparterial 
bronchi, nor in what manner the existence of these is to be ex- 
plained. It is, however, certain that if the human lungs originally 
bore homologous superior lobes, this symmetry must have been 
early lost. In face of these facts it is idle to speculate as to 
probable causes which may perchance have effected a gradual loss 
of symmetry of the bronchi. 

^ Kg. BradypuSf UquiLS, UkpJias, Phoca^ Phoccena communis f Delphimcs delphis, 
and Aiichenia. 

^ The presence on both sides of an eparterial bronchus has only twice been 
observed in Man — once where the viscera were in the normal position, and once in a 
case of situs inversus. In both instances there were also marked anomalies of the 
trunks of the larger arteries in the thorax. On each side three well-defined pulmonary 
lobes were found, and bilateral symmetry was complete (Dalla Rosa). 

Complete absence of the eparterial bronchus, and the existence of a tracheal near 
a bronchial eparterial bronchus, have been observed in Man. In the latter case, 
according to Chiari, it would appear that one of the collateral (dorsal) branches of 
the normal bronchial eparterial bronchus had become independent, and wandered 
up to the trachea. This view receives support from the well-known tendency 
of the lateral bronchus to give up branches to the principal, and from the 
study of cases in which two eparterial bronchi, one above the other, are found. 
The upper of these is evidently a branch of the ordinary eparterial bronchus 
shifted on to the main bronchus, and in this phenomenon we have an intermediate 
stage between the normal condition and that of the tracheal bronchus. The 
latter may therefore be regarded as a branch of the ordinary eparterial bronchus 
which has wandered farther up. I put forward these views with all reserve. 

[His has shown that in Man the first hyparterial bronchus of the left lung divides 
immediately after its origin, giving off an ascending branch (unrepresented on the 
right side) which runs forwards to the apex of the lung. Robinson has shown {Jour. 
Anat, and Phys.^ vol. xxiii. p. 240) that the same is true of the Rat, and he suggests 
that this ascending branch may, as it were, compensate for the absence of a distinct 
eparterial bronchus.] 



THE ALIMENTARY CANAL AND ITS APPENDAGES 177 

In dealing with the lung of the Primates, considerable 
importance attaches to the growing together of the pericardium 
and the diaphragm, for this brings about a constancy, or, if I 
may be allowed the expression, a certain rigidity in the form of 
the pleural cavities. As a consequence of this, a stricter limit is 
placed upon the extension of the lobes of the limgs than in the 
lower Mammals, in which the lung is able, either constantly or 
during inspiration, to penetrate between the heart and the 
diaphragm, into the sinus subpericardiacus. This applies especially 
to the right limg, at the base of which a special lobe may be 
more or less distinctly developed. This, the lobus subperi- 
cardiacus (or azygos impar), is occasionally present in Man, 
most frequently, it appears, in the lower races and in micro- 
cephalous individuals. The probability that its presence may 
be indicative of atavism is not lessened by the fact that indica- 
tions of it often occur, in the form of a blunt process lying in 
front of the ligamentum pulmonale, which sinks into a depression 
in the mediastinum, just as in the Orang. 

Hasse has not only confirmed Aeby's observations in all 
essential points, but, by the aid of very ample material, has 
extended and revised them. According to him, the principal 
bronchi of the human lung run downwards, backwards, and 
slightly outwards, the direct current of inspired air following the 
same course. He raises the question whether this has always 
been the disposition of these bronchi, and inquires into its cause. 
The first question he answers in the negative, and seeks to prove 
that a very gradual change took place in the position of the 
bronchi ; indeed, that the position which has been acquired in 
the course of Phylogeny is exactly the reverse of the primitive one. 
The facts discovered by His in the study of the hiunan embryo 
lend support to this view. In other words, comparison of the 
embryonic with the adult condition shows most clearly that a 
depression of the right and an elevation of the left chief bronchus 
takes place. The condition of the adult, so far as the branching 
of the bronchi is concerned, is effected as early as the end of the 
second month of intra-uterine life, the change being in the main 
due to the twisting of the heart upwards, backwards, and to 
the left. 

Hasse is, however, unable to prove any more satisfactorily 
than his predecessors why the right lung-sac is from the first 
more spacious than the left, and what caused the right eparterial 
bronchus to appear. He has, however, made an attempt at 

N 



178 THE STRUCTURE OF MAN 

explanation which, since it appears to me to possess a certain 
degree of probability, may be here recapitulated. He vprites : 
" Since the heart and its immediate connections push the right 
primary pulmonary sac, which from the first is larger than the 
left, backwards and upwards, the branches of the fifth aortic arch 
— the arterise pulmonales — (which, as fig. 1 5 in His's work shows, 
descend quite symmetrically) come to lie somewhat diflferently 
on the two sides. The right artery must cut across and overlie 
the primary lung-sac earlier than the left, and become therefore 
the sooner connected with it. Herein, perhaps, also lies the 
explanation of the greater growth of the right sac, and of the 
fact that this gives rise to a special outgrowth, the foundation of 
the eparterial bronchial system. I am the more inclined to this 
belief, and to that in the above-named determining causes, by the 
fact that in cases of dtus inversus and reversal of the heart and 
great blood-vessels, the relationships of the right and the left 
main bronchi, and indeed of the two limgs as wholes, are also 
reversed (Weber, Leboucq, Aeby)." 

This is not the place to consider further either the relationships of the 
bronchial system, the differences in its distribution in relation to the planes 
of the body, or the changes which it undergoes after birth. For these 
details I must refer the reader to the original monograph. In the same 
work is to be found a discussion of the arrangement of the bronchial system 
in adult human beings, the explanation of which may be summarised as 
depending upon the direction of movement of the single points of the 
thoracic walls lying round the lung. Hasse concludes his interesting account 
as follows : — " If it be admitted that the tendency towards modification 
conditioned by the mechanism of the walls of the thorax is inherited, then 
we must allow that the facts point back to the form of lung of the earhest 
ancestors of Man among the Amniota, and to the changes which the respirat- 
ing organs have gradually undergone in the course of time in the ancestral 
series. The principal direction of the bronchi is at first downwards and 
backwards. From this it follows, it seems to me, that in the ancestors of 
Man the diaphragm first played the principal part in respiration. Then 
the system of branches running outwards and downwards is developed in an 
ascending degree. From this I conclude that thoracic respiration next super- 
vened in increasing degree, this being most marked in the lower, or better, 
the posterior part of the thorax, and least marked near its upper and anterior 
region. By degrees the upper and anterior part of the thorax took an 
increasing part in respiration, and this led to the mechanism of respiration 
which is illustrated in Man. This course of the development of respiration 
and of the respiratory movements, it appears to me, is in exact correspond- 
ence with the development of the respiratory organs as I have explained 
them, and with the facts brought to light by Aeby's investigation of the 
bronchial tree of the lower animals." ^ 

^ I put forward these views of Hasse with all reserve, and I would draw attention 
once more to a point already touched upon in dealing with the thoracic skeleton 



THE ALIMENTARY CANAL AND ITS APPENDAGES 179 

(ante, p. 43), i.e. the structural variation of the first rib, and the feeble respiratory 
activity and consequent slight movement of the tips of the lungs. I consider that 
these phenomena should be regarded as degenerative, on the assumption that the 
remote ancestors of Man were still provided with cervical ribs, and that their lungs 
extended farther towards the head than they now do. There must thus, as I think, 
have been effected in the Phylogeny of Man first a shifting of the respiratory organs 
in a caudal direction, and next in order the formation of the diaphragm, and, in 
connection with the latter, a modification of the respiratory mechanism originally 
restricted to the lungs and the walls of the thorax. The contrast between this 
theory and that of Hasse is obvious, and although I am as little able as he is to 
furnish proofs, I believe that my explanation receives support from the facts of 
development and Comparative Anatomy. 



THE CIECULATORY SYSTEM 

In no other system of organs does the fundamental law of 
biogenesis find such wide application as in the circulatory, and 
to go into details concerning it would be merely to repeat 
what has been often said before. Attention may therefore be 
confined to the following facts. 

The Heart 

The heart arises {cd., Fig. 31, A), at an early embryonic 
stage, far forwards in the cervical and indeed in the cephalic 
region. This recalls its position in adult Fishes and Amphibiana 
The comparison with these animals is the more fully justified, 
in that the heart of the early human embryo, like that of the 
lowest Anamnia, has throughout a single lumen, and its further 
difierentiation is gradually undergone in correspondence with the 
phylogenetic development of the organ. 

The structure of the heart, originally very simple, soon 
becomes complicated, but even then certain peculiarities of the 
right auricle point back to the condition found in the Amphibia. 
These are, for example, the inconstant vestiges of valves at the 
opening of the left vena cava superior (Thebesian valve), and 
the almost constant remains of the valves of the sinus at that of 
the vena cava inferior (Eustachian valve). The same applies to 
the traces of the incorporation of the sinus venosus and of the 
pulmonary veins into the opposite divisions of the atrium 
(auricles). In short. Comparative Anatomy furnishes not only 
interesting parallels with, but an explanation of the various stages 
in the Ontogeny of the heart of the higher Vertebrata. There 
are, however, some conditions which occur in the Mammalian 
heart, especially during the early periods of its development, 
which cannot be explained by inheritance, but which have arisen 
secondarily through adaptation ; among the chief of these are the 



THE CIRCULATORY SYSTEM 181 

secondary perforation of the septum atriorum and the formation 
of the annulus ovalis or isthmus of Vieussens. 



The Arterial System 

The arterial system of Man bears traces of primitive con- 
ditions. It is indeed an astonishing fact, for example, that the 
aortic arch system of the embryos of the higher Vertebrata, up 
to Man himself, appears in the same manner as in the Anamnia. 
Six pairs of aortic arches in all are formed in the young 
Mammalian embryo, but the representatives of the first and 
second of these and the vestige of the fifth degenerate early ,^ and 
consequently only three pairs remain to undergo final transfor- 
mation. 

[Conspicuous among the variations occurring in Man is the 
occasional presence in the adult of paired aortic arches, the arch 
of the right side, which usually disappears during development, 
being retained. Twelve cases of double aortic arch have been 
recorded in Man,^ and this variation may be accompanied by the 
obliteration and reduction to a fibrous band of the ordinarily 
functional (left) arch,^ the resulting condition of the parts being 
essentially that characteristic of Birds.] In a similar manner, 
many of the variations to which the vessels derivative of the 
primitive arterial system of the human embyro are liable, can 
only be explained by the fact that embryonic trunks, which 
imder normal conditions become occluded and vestigial, may 
remain functional throughout life. In this respect the Anthro- 
poids altogether agree with Man. 

On the inner surface of the abdominal wall in Man three 
cord-like structures pass from near the bladder to the navel. 
These are known as the ligamentum vesicale medium and the 
ligamenta vesicalia lateralia. The first urachus corresponds witli 
the stalk of the allantois of the embryo ; the latter, however, 
are the last vestiges of the umbilical or hypogastric arteries, 
which during intra-uterine life, i.e. from about the time when the 
posterior limbs are just beginning to appear as buds, convey the 

^ [The recent researches of Boas and others have proved that in all classes of 
terrestrial Vertebrates the pulmonary artery is a derivative of the sixth aortic arch 
(the fourth branchial), and that the arch in front of it is suppressed ; and Zim- 
mermann has shown that Man himself is no exception to this rule {Verhandlg. 
Internal. Medic. Congresses X.^ Berlin, 1891, Bd. ii., Abth. i. p. 145).] 
2 [Cf. Leboucq, Ann. Sci. Med. Oand.f 1894, p. 7.] 
^ [Cf. Morrison Watson, Jour. Anat. and Phys. , vol. xi. p. 229. ] 



182 THE STRUCTURE OF MAN 

blood from the aorta to the placenta. The basal portions of these 
vessels often remain patent throughout life, and fimction as 
superior vesical arteries ; the remainder of each, however, i,e. by 
far its greater portion, loses its lumen altogether and becomes 
a solid strand of connective tissue. 

[Considerable interest attaches to those veins of the very 
variable *' vesico-prostatic plexus " which, in the adult, in proxi- 
mity to the above-named arteries, carry back the blood from the 
urinary bladder to the internal iliac veins. The detailed re- 
lationships of certain varieties of these would seem to suggest, 
by analogy to the lower vertebrata, that they may be associ- 
ated with the "anterior abdominal" venous system regularly 
present in Birds, Eeptiles, and Amphibians, and represented by 
at least its main trunk, in the Monotreme Echidna^ among 
Mammals.] 

The continuation proper of the axis of the human aorta 
is represented by a weak vestigial vessel, of very variable 
relationships ^ — the arteria sacralis media. In long-tailed 
animals, in which the posterior end of the body has not 
undergone reduction, this vessel is represented by the caudal 
artery, which is a direct, gradually diminishing, continuation of 
the aorta, originally giving off, like it, segmentally recurrent 
branches. 

When we consider the polymeric origin of the limbs (cf. ante, 
p. 67) dating back to an originally segmented condition of the 
trunk, it is evident that their principal arteries must have arisen 
in relation to segmental arteries of the body wall, and that 
originally they in no way differed from these. This assumption 
finds actual proof in the mode of origin of the arteria subclavia ; 
but while it is comparatively easy to prove this for the fore- 
limb, in the hind-limb a difficulty presents itself, since its corre- 
sponding vessel at a very early period undergoes a great increase 
in size and marked specialisation in relation to the development 
of the umbilical artery.^ In any case it is certain that the 

^ [Cf. Fenwick, Jour. Anat. andPhys., vol. xix. p. 320 ; and Beddard, Proc. Zool, 
Soc,, Lond., 1884, p. 553.] 

* [These have been recently tabulated for 400 autopsies worked out by coUectiye 
investigation in medical schools, under the auspices of the Anatomical Society of 
Great Britain and Ireland. In one instance the vessel appears to have been entirely 
absent, cf. Jour. Anat. and Phys.y vol. xxvii. pp. 184-187.] 

* I cannot here enter further either into the question of primary origin, direct 
from the aorta, of the arteria umbilicalis, or into that of the secondary connection 
between this vessel and the arteries of the limbs. It must suffice to refer the reader 



THE CIRCULATORY SYSTEM 183 

artery known as the common iliac is the first formed of the 
posterior limb, and that it arises as a segmental vessel of the 
aorta. 

The artery which, in the embryo Mammal, including Man, 
runs into the developing posterior limb bud, does not directly 
become the arteria femoralis of the adult. It accompanies the 
ischiadic [or crural] nerve in its distribution ; on the posterior 
side of the limb it runs down to the bend of the knee, and from 
this point is continued into the upper part of the thigh. This 
artery should be called the ischiadic [or crural] as it corresponds 
with the vessel of the same name in most Birds, and with the 
principal vessel of the hind-limb in Eeptiles and Amphibians. 

" The femoral artery develops later as a branch of the iliac. 
At first it spreads only over the inner or ventral portion of the 
thigh ; it, however, soon grows rapidly in a distal direction, along 
the inner surface of the cartilaginous femur, to the bend of the knee, 
where it unites with the ischiadic artery. The femoral artery 
thus formed rapidly increases in size, while that section of the 
ischiadic related to the upper leg degenerates. It is thus 
that the definitive condition is attained ; and but a short vestige 
of the arteria ischiadica persists in the adult, as the " ischiadic " 
or " inferior gluteal " (Hochstetter). Mechanical causes may have 
perhaps brought about this change in the principal artery of the 
hind-limb in the ancestors of Mammals, but we have no clear 
knowledge on the subject. 

In no other part of the body are the variations in the arteries 
so frequent as in the fore-limb, especially in the hand. The 
arteries of the foot present numerous variations, and, in correla- 
tion with the variations of the skeleton and musculature, 
some of these may be classed as progressive and others as 
retrogressive. 

Where a supracondyloid process of the himierus exists (cf. 
ante, p. 78) the brachial artery lies behind it. The latter is 
thus covered by the head of the pronator teres muscle which 
extends upwards, and the condition resembles that of those 
Mammals in which the brachial artery and median nerve pass 
through an invariably developed foramen supracondyloideum.^ 

A comparison of the arteries of the hand with those of the 
foot shows that there are in the hand two palmar arches, a 

to the recent series of very careful studies by Hochstetter, published in the Morpho- 
logisches Jahrbtich, 

^ For further details on this point, cf. Ruge, Morpholg, Jahrb., Bd. ix. p. 329. 



184 THE STRUCTURE OF MAN 

deeper and a superficial, but in the foot only a deep plantar 
one. It is evident on reflection that a superficial arch cannot 
exist in the foot on account of its functions as an organ of 
support, and that the larger pedal arteries, to be free from 
interference with the circulation, may have had to withdraw 
into the recesses of the foot. Indications, however, are not infre- 
quently encountered that the foot formerly possessed a super- 
ficial arterial arch, and that the arteries for the toes arose from 
it, in a manner identical with that in which the arteries for 
the fingers arise from the superficial palmar arch of the hand. 

Finally, as to the intestinal arteries, although our knowledge 
of the development of these is still very limited, all things point 
to the fact that originally they were numerous and segmental, 
and that their final reduction in Man and Mammals to three 
trunks, the cceliac, omphalo-mesaraic (which later becomes the 
superior mesenteric), and the inferior mesenteric, is to be con- 
sidered as secondary. 

The Venous System 

The developing venous system of Man, like the arterial, 
shows unmistakable traces of a very primitive condition inherited 
from the lower Vertebrates. In this connection the anterior 
and posterior cardinal veins, the ductus Cuvieri, and the sinus 
venosus cordis, are especially conspicuous. 

The system of the vena cava inferior is a late acquisition, 
dating [in its fully differentiated form] from the higher Fishes 
(Dipnoi) and Amphibians. Its phylogenetically recent origin 
is, even in Man, denoted by the variation and arrested develop- 
ment which it occasionally exhibits. Several cases of [that which 
Hochstetter's researches prove to be] the persistence of an early 
stage in its development have been recorded. I refer to those 
in which the caval vein, from about the level of the superior 
mesenteric, is continued downwards towards the pelvis, owing 
to the retention of the posterior cardinals. 

In these cases we may speak of persistence of the posterior 
cardinals in the form of a double vena cava inferior. 

In other cases of what we may now regard as arrested develop- 
ment, the distal portion of the inferior vena cava is formed out 
of the left instead of the right cardinal vein, there is then a 
vena cava inferior passing to the left [of the aorta]. 

In very rare cases, where development is arrested at a very 



THE CIRCULATORY SYSTEM 186 

early stage (eighteen to twenty-one days after fertilisation), the 
post-caval vein never develops, and the posterior cardinals take 
its place. 

In one such case, described by KoUmann, the two posterior cardinal 
veins persisted to the level of the third lumbar vertebra. At the crura of 
the diaphragm, within the aortic foramen, the right cardinal vein was con- 
nected with the left by three branches. The trunk thus related lay to the 
left of the aorta, and ran on as a persistent portion of the left cardinal. At 
the level of the tenth thoracic vertebra the vessel turned to the right, and 
after this it was the right cardinal vein which was continued to its point of 
entrance into the vena cava superior. The ductus venosus Arantii was absent ; 
and the circulation in the liver remained entirely embryonic, the hepatic 
veins still entering the heai*t separately. This remarkable case was that of 
a man of twenty-eight, who had committed suicide. 

In Man, and certain Mammals (Apes, Lemurs, Carnivora, 
Whales, and Edentates), the left vena cava superior early degener- 
ates and disappears, with the exception of its basal portion, which 
remains as "the coronary sinus," so-called on account of its 
receiving the intrinsic cardiac veins. [The great veins of the head, 
neck, and fore-limb on the left side become connected with those 
of the right by a transverse trunk, derived from the left innomin- 
ate vein — the two innominate or brachio-cephalic veins uniting 
to form the single " superior cava."] In this we have to deal 
with the modification of a condition which in other Mammals 
(Eodents, Insectivora, Bats, and Ungulates) is retained throughout 
life ; [and it is an interesting circumstance that among these a 
transverse connection between the great veins of the neck strongly 
suggestive of that above described may not infrequently be estab- 
lished (ex. Lejpus), without any accompanying reduction of the 
left pre-caval.] 

The venous system, so rich in variations, is well known to 
possess valves which prevent regurgitation, [and thus ensure the 
maintenance of the single circle of the circulation.] In keeping 
with this we should expect to find such valves chiefly in the 
limbs, i.e. where the venous stream — I refer especially to the lower 
limbs — already has great difficulties to overcome. This expecta- 
tion is fulfilled ; but when we reflect that the ancestor of Man 
himself had a quadrupedal ancestry, it follows that there must 
have been a time in which his thoracic, and abdominal, and dorsal 
surfaces, now disposed antero-posteriorly, were turned downwards 
and upwards and were disposed ventro-dorsally. Circulation within 
the intercostal and limibar veins must then have been placed under 
much less favourable conditions than at present ; it had to be 



li^ THE BTBUCTUBE OF JIA3: 

umnMimd, as tbe v^^k^us i-ireuiatiQxi in the iawex limbs now has, 
Hjffiimi the iMX'ym <A gravity. Tim justi£abk afiBnmptaon has led 
m^ U; iiiv<^iga.t(i tl>fc iixUsror/stal veixu? in Man closely, by way of 
aHcerUiiiiJug if tti^y po46se^ v^ve6^ axMl my obserraticHis in all 
etsM^eutiiili^ (jmtirui ih<^^ of tl^^ile recx/rded in his Handhwch der 
A'fudorrde, TJ^at i«, I found great variation both in the number 
miA i\iH di^velopr/^nt of iXih valves, so that the impression of a 
retrogivKttwive iMiiAiium \)eeiiiae irresistibla 

J t iti wfell kwown tliat in other parts of the body, valves of 
Hid vtiinH ttp[>ear m a reduced and evidently degenerating or 
VB«tJgittl form, and also tliat in the embryo there arise many 
liKU'ti vttlve« than attain complete development. [The valves of 
tliB [HiiUl ByHtem arc among the number thus suppressed, but 
thtiy uiay lie occaHionally retained.^] 



The Spleen 

Throughout tlie Mamraaliau series three lobes of the spleen 
mny he tlatet^ted, viz. uu anterior, a posterior, and a middle, all 
of whioh vary gvmtly in nize uud form, in the various types. In 
MuvaujiiulH tlie poHttniov lobe stretches far down towards the 
vtH^tuu^. In tlio Phunnital mammals the lobes are increasingly 
ivd\u*tHl, uml tiuaUy, iu the Primates, the posterior lobe has 
ahm^at ilisi^j)*\veaivil ; but the anterior and the median are repre- 
aca^tiHl ^\K^\ iu Man, while the jH>8terior lobe is in him reduced to 
a jao>vti<.a\ of ita u^ai*go obtusus (KlaatschX 

The average weight of the spleen in the white races is said 
lo l»e IV>C>. auvl iu the black but 171 grs. 

tht^ W'iiiiclii vKt %\x^ tiU'g«> iuWiitiu^ Aft^r birth tb^y <lii»p(>eftr r&pidlj, and wken 
^^^'ut iu t,ht) ^ult %h*»\ a(K^>eair W \>^ itto^ abuudii&t on tJbs smaU inteetiiK. C£ 
BvK?hiiWtWJf, A'xMv /\ .ifujU. Hfui M^&, 1$37 ; Anui. Alfih,y p. l^T; and B^yant^ 
HuaJiOii MetiiojU (*^ui Sufykal Joarnaly vol. cxix. ^ -400. Hyrtl long 9gp ^r»w 
i^tt*jutivu i,A>ii^ttM(/^, ^'iett^ Akiid.y BiL IxL }h t7^ Ixt the exidtenc^ in t&e 
s4 ik !i\}ii)d \iil\^'}ik^ told withiu th*> pgrtsJl v*jiu.] 



THE URINOGENITAL SYSTEM 

The Pronephros and the Primitive Kidney 

In all classes of Vertebrates the Urinogenital System first appears 
[in the form of a duct (Wolffian or Segmental duct) which is 
primarily related to a urinary apparatus confined to the head 
region. In the Amniota and Selachii the latter is wholly de- 
generate in character ; among the remaining Anamnia, however, 
it may for a longer or shorter period persist as a distinct first- 
formed functional excretory organ. It is accordingly regarded 
as a possible larval kidney, and termed the pronephros, as it 
appears to be of very ancient origin]. While the secreting 
glandular portion of this system never lasts for more than a 
short period, its duct persists and appears in some cases (cf. 
infra, p. 190) to give rise to the leading duct of a much more 
extensive urinary system that develops later and is known as the 
middle kidney or mesonephros. 

This second nephridial system, which becomes the definitive 
urinary system of Fishes and Amphibia, consists like the pro- 
nephros of metamerically recurrent tubes. The two systems 
are so constituted as to suggest for the Vertebrata of to-day an 
origin from a lowly segmented ancestor.^ 

The higher Vertebrates pass through an embryonic stage, in 
which they possess first a pronephros and then a mesonephros, 
which is an irrefragable proof that in their ancestors, and con- 

^ [This view receives support from the general tendency towards corresponding 
metamerism of the muscular, skeletal, nervous, and vascular systems of the vertebrate 
body. There are, however, reasons for thinking that the recurrent symmetry of at least 
the skeletal and muscular apparatus may be of secondary significance ; and there are 
not wanting competent investigators who deny in toto the origin of Vertebrates from 
multi-segmented animals (cf. especially W. K. Brooks "The Genus Salpa, " i/cm. 
Biol. Lab,, Johns Hopkins Univ., II. pp. 182-203). The whole question must remain 
in abeyance, pending further inquiry into the origin of metamerism in general, with 
a view to the formation of a sounder conception concerning that.] 



188 THE STRUCTUKE OF MAN 

sequently in the ancestors of Man, each of these organs once 
constituted in turn a permanent urinary system.^ 

[The definitive kidney and ureter of Mammals arises at a com- 
paratively later period (eleventh to twelfth day of intra-uterine 
life) in relation to an outgrowth of the base of the mesonephric 
duct.^ This kidney, by extension, reaches to the mesonephridial 
region. On account of its distinct origin from the rest of the 
excretory system it is generally termed the metanephros, and its 
duct the metanephric duct.] 

The definitive adult kidney of Man is, as a rule, a compact 
organ, with smooth walls; but its surface is not infrequently 
more or less distinctly furrowed, and thus apparently lobed. 
Lobation of the kidney is characteristic of certain lower Mammals 
[e.g. Cetacea and Ungulata]. The regular appearance of furrows 
in the kidney of the human embryo, giving rise to the so-called 
"renculi," and the not infrequent ocQurrence of an increased 
number of renal arteries, justify the conclusion that the lobate 
structure may have been typical of the ancestors of Man. 

It is not yet evident what first led to the degeneration of 
the pronephros and to the loss of a renal fimction by the 
mesonephros in the amniota. So far as the mesonephros was 
concerned, the degeneration did not originally affect the whole 
organ, but only a part of it. The remainder, undergoing a change 
of function, became secondarily related to the male reproductive^ 
apparatus. It gave rise with its duct to the epididymis and 
vas deferens, and became otherwise transformed into a series of 
vestigial appendages to the urinogenital organs of both sexes. 

^ This view, so far as it involves the conclusion that the mesonephros of the 
Amniota is the representative of the excretory organ of their ancestors, receives 
its chief support from the condition of the excretory apparatus in Reptiles. These 
animals pass through a period in which the greater part of the mesonephros con- 
tinues functional, side by side with the later definitive kidney. In the Lizards, for 
example, it shrivels up after the first hibernation, i.e. in the second year. 

2 [The metanephric tubules of Mammals are stated to arise as outgrowths of this 
diverticulum itself, but in other animals there is good reason for regarding them as, 
at any rate in part, distinct in origin — i.e. as arising independently of the duct 
with which they subsequently become connected, in the manner typical of the meso- 
nephric series. The recent researches of Semon (Jenaische Zeitschrift, Bd. xxvi. 
p. 89) and Field {Bullet. Mils. Coinp. Zool. Harvard^ vol. xxi. p. 201) have revealed 
striking details of similarity in development between the pro- and meso-nephridia, 
rendering it more difficult than hitherto sharply to discriminate between them. 
Indeed, recent discovery tends to suggest that the pro-, meso-, and meta-nephridia 
are portions of one continuous system, and that their apparent independence is due to 
the assumption of secondary relationships with independently formed ducts.] 

^ The initial stages in this process have been permanently retained as the adult 
condition by the Elasmobranchs and Amphibia. 



THE URINOGENITAL SYSTEM 189 

In the wholly vestigial condition the mesonephros is not infrequently 
the seat of origin of pathological aflfections (formation of cysts). 

The vestigial portions of the mesonephros in men are 
the paradidymis, Girald^'s organ, and the stalked hydatids of 
Morgagni; in women it 'gives rise to the greater part of the 
parovarium and the whole of the paroophoron. Further, in 
women, the last vestiges of its duct are found, either confined to 
the region of the parovarium, or, where suppression is least 
marked, in the form of "Gartner's canal" which reaches the vagina. 

MijLLKRiAN Duct 

Van Wijhe, believing that the ancestors of the vertebrate were 
hermaphrodite, has argued that the first appearance of the Milllerian 
duct probably dates back to a period in the evolution of the phylum 
when, as a means of preventing self- fertilisation, there were 
distinct ducts for the transmission of the sperm and the ova. Be 
this as it may, the secondary nature of the Milllerian duct is 
shown by its comparatively late development in the individual 
It originates in the Amniota by evagination of the ccelomic 
epithelium, to form a structure which, becoming constricted off 
into a tube, gradually elongates in a caudal direction to reach 
the cloaca. 

In the male, the duct of the mesonephros, and in the female, 
as is well known, the whole of the Mlillerian duct, forms the 
adult genital duct (c£ Fig. 103). In the male the greater part 
of the Mlillerian duct degenerates or entirely disappears, thus losing 
nearly all physiological significance. Its proximal vestige becomes 
in Man the unstalked hydatid of Morgagni, a small appendage of 
the testis ; its distal end, however, is believed to unite with that 
of its fellow of the opposite side to form a vesicle, the " uterus 
masculinus," which becomes embedded in the prostate, and later 
opens, conjointly with the vasa deferentia, into the urinogenital 
sinus (urethra).^ 

^ [The term ** uterus masculinus" is applied, by analogy, to a somewhat 
similarly placed median vesicle, opening into the prostatic portion of the urethra 
in other Mammals. One well-known case is that of the common Rabbit. The 
so-called " uterus masculinus " of that animal certainly does superficially resemble 
that of Man, but the two differ fundamentally in their relationships to the vasa 
differentia, i.e. in Man the bases of these pass behind the vesicle and open at its 
sides, while in the Rabbit they pass in front of it and open within its anterior lip. 
Kblliker from the study of its development, has claimed for the so-called " uterus 
masculinus" of the Rabbit) {Enticickhingsgesch. d. Menschen n. d. hohern Thiere^ 



,*:--«gO| 



^? <?? 



'c-Vl 



</2 '■ 





THE UEINOGENITAL SYSTEM 



1»1 



Fta. 103.— A SBKIBS of WKOLLT DlAQEtAUUATIC FlQORES T 
COHPAHATIVB MOHFHOLOGT OF THK URINOOBNIIAL OBOAKB OF THK VbKIEBRJTA. 
A, ThepronephiDs gtageof tbe ADamuia; B, h later stage of the game ; C, the imiic^nital 
apparatus of the maJe Amphibian ; D, the lame of the female ; £, proDephrog 
stogeottbe AtnDinta, the mesoDeplirDS as yet niilinieatHrj ; F, urinogeiiitat apparatus 
otthe Amniota, at a stage at which the seies are not dilferentialfid ; G, uriliogonital 
apparalua of the male Aniiiiota | H, the same of Ihe fenjale ; p.n,, pronephros ; 
d.jm., duct of the pronephros ; nu., the developiug mesonephros ; taa.s,, part of 

-VBstigea of the mesonephroa, the paradidymis and the paroophoron ; 't, rets and 
vasa eSerentia testis ; 'H', a network homologous with these structures at the hitua 
ovarii ; %»., stalked hydatid ; ms.r., portion of the meaonephros which in Amphi- 
bians and Selachians becomes the so-called pelvic kidney; d.ms., duct of the 
mesonephros, which in male Ampbibinns and Selachians becM>nies (Fig. C) the urina- 
genital, and in feniales (Fig. D) the urinary dnct. In the male Amnlota it gives 
rise to the seminal duct (Fig. G), and in the female to the Gartner's duct (Fig. H). 
B.s., the Beminal Teeicle. an outgrowth of the dnct of the mesonephros ; d-m., 
MUllerian duct, which in Mammals becomes ilifferentiat<d (Fig. H) into the Fallopian 
tubat;!.), the uterus («(.), and the vagina (vg.); os., its ostium abdomiuale tubra ; 
Ay. and u.m. (Fig. O), unstalked hydatids and uterus masculinus (vestiges, in the 
male, otthe Mlillerian duct, d.m.) ; inf., the defluitive kidney or nietanephros of the 
Amciota, asserted to arise from the ureter (ur.), itself an out^owth of the mesonepbric 
dnct ; a/'., allantois (urinary bladder) ; sn., sinus urogeuitalis ; P-9-, genital pco- 
minenca ; g.g., genital glands, undilTerentiated stage ; ot>., ovary ; Is., testis ; cl., 
cloaca ; oL, hind-gnt ; p.a. , poms abdominalis ; g.c, Cowper'a glands. 



Tabulated BisunU of the Facts •pictorially illustrated on the 
opposite Page. 



A..,..!., 


AmiitoU. 


1 

n 


Develops in all Anamnia, but in 
all probability never [wrsists as 


Still develops in the Aniniota, but 
as an exci-etory organ undergoes 


" 1 

1 i 


origin by subdivision to both Probably persists as the Mesoneiihric 
Mesonephric (Wolffian) and Mul- (Wolffian) duct, and contri(,nt«a 
lerian ducts. In Amphibia, he- in aoma to the formation of the 

phric duet Its fato in other of inf«rpretation still esist con- 

Anamuiik is not yet fnlly investi- ! cemiug it, 

gatod. 


(i 'Functions in all Anamuia as a Loses its riiual function in all 

8 g ' Amphibians, and one or two and becomes vestigial, except so 
g. *• higher Fishes, its anterior por- far as it becomes an accosaory 

g ■ . laale genital ap()aratu3, the jios- atus in the male, [and ent<M'B into 
a *! 1 t«rior portion iiersiatinK 03 a pel- the formation of the anprarenal 
la ' manent kidney. • body.] 



THE STRUCTtTRE OF MAN 





Amunnla. 


Amnioti. 




^ 


The proximal podJOD becomos in 
most related ta tbe testis, and 
fimetionsl in the traiiBTuission of 
tlio semon, tho distal funi^tiouing 
ag a kidney.' 


The proximal end becomes tbe rete 
and vasft eHerentia testis, and tbe 
caput epididymis, and psrbspa 
also the sulked hydatid of Mor- 


Fersiata ^ tbe kidney. 


The greater part of the proximal 


i 

•a 

1 

a 


4 

1 


FuQctions in moBt higbar Fishes 
merelj as tbe urinary duot. 

some Canoida, seivea ae the 
urinogenitttl duct. 


The proximal portion becomes the 
corpus and cauda epididymis, and 
the distaJ tbe aommal duct (yaa 
deferens). 


Fmiction.^ exclusively as thediiGt of 
the ineaonejihroa, i.e. the urinary 
duct. 


The greater part, as a rule, degener- 
ates ; the proximal portion may 
be retained in a vestigial form iu 
the region of the parovarium. In 
certain cases it may porsifit as a 
whole, as Gartner's canal. Tlie 
distal end becomes the orsau of 
Weber. 


5 

S 


1 


In Elasmobmuchs. for certain, it de- 
generatGK in post- embryonic life, 
vestiges of its prosiraal portion 
being retained. (Its fate in most 
other Fishes ia doubtful.} InAm- 
iibibiii it is retained for its whole 


The prosima! portion becomes the 
unstalked hydatid of Morgagni, 
tho distal, in some Mammals, tbe 
so-called "uterus maBCulinua. " 
In exceptional caaes tbe whale is 
retained as Ratbke'a duct In 
Sauropsida tbe distal partnsually 
disajipears. 


Becomes tbe whole genital duot 


Becomes the whole genital duct. 


1 

•a 


1 

1 
1 




Dovelopment not yet fully worked 
out. It appears to arise in part 
(ureter) from the distal end of 
the mosouephric duct, and in 
part {secreting elemenfa) as a 
caudad extension of the roeao- 
nephroa. 



' [The males of the Bony Fishes and of the Maisipobranchii are exceptions to 
this nile, the mesonepbros being in them f\inctional only as a kidney]. 

' [Allowance being made for its entering into the constitution of the supraranal 
body (of. previous page).] 



THE URINOGENITAL SYSTEM 



193 



In Amphibia, Eeptiles, and Birds, the Miillerian ducts in the 
female remain separate throughout life, and this is also the ease 
in the lowest living Mammals (Monotremata), which are partly 
on this account called the Ornithodelphia. In all Mammals above 
the Monotremes, however, they early become to a lesser or greater 






Fig. 104. — A to C, Diagrammatic Representations of the Chief Types of Uterus 

OCCURRING IN THE PLACENTAL MaMMALS. A, UteRUS DUPLEX ; B, UtERUS 

Bepartitus ; C, Uterus Simplex ; D, Urinogenital Apparatus of a Female 
Musteline ; B, the same of the Hedgehog, the former with Embryos (* *) 
in the Uterus. 

od.f oviduct (Fallopian tube) ; ut.j uterus ; ut',j cornua uteri ; ut"., corpus uteri ; vg., 
vagina; ot., ostium tubae ; gL^ accessory gland; r., rectum; s.ug.^ sinus urino- 
genitalis ; re' .^ kidney ; re"., suprarenal body ; wr., ureter ; hi., bladder. 

Aufl. II. p. 981) a paired origin from tbe bases of the mesonephric ducts, and in 
respect to this it exactly harmonises with, and would appear to represent in a 
confluent form, the human vesiculae seminales. The fact that among other Rodents 
it is represented {e,g, Guinea-Pig) by a pair of elongated coeca, or {e.g. Muridae) 
by two folded and more glandular diverticula, having the detailed relationships of the 
seminal vesicles of the other mammalia, fully bears out this view. — G. B. H.] 





194 THE STRUCTURE OF MAN 

extent united, the union being first effected at a middle point, 
before the ducts themselves open into the urinogenital sinus. 
[Those portions of the oviducts situated above this point of union 
become converted into the uteri and Fallopian tubes, and those 
below into the vaginae.] 

Among the Marsupials there arises at this point a median 
vaginal sac, and neither the upper (uterine) nor the lower (vaginal) 
portions unite further. For this reason these animals are fre- 
quently classified as the Didelphia. In all the higher and truly 
placental Mammals the union extends backwards to form a 
single median vagina [as is expressed in the application to them 
of the term Monodelphia]. It also extends forwards, giving rise 
to a single median uterus as we ascend in the series (cf. Fig. 
104). Man and the Primates are among those monodelphous 
Mammals in which the two u{eri as a rule completely unite: 
but abnormal forms of uterus, known as uterus duplex, bilocularis, 
subseptus, bipartitus, incudiformis, arcuatus, and bicornis, not 
infrequently occur, at any rate in Man. These are but the 
expression of arrested development, — arrested, that is, at stages 
corresponding with those of the gradual fusion of the originally 
separate Mtillerian ducts effected during the course of long 
geological periods. The uterus simplex is the normal condition 
in the Primates of the present time. 

In the uterus simplex, traces of the primitive paired condition 
of the Mtillerian duct are still found in the paired Fallopian 
tubes {od., Fig. 104, C), and in the longitudinal ridges of the 
cervix uteri and of the vagina (columnae rugarum). 

Hymen 

The primitive significance of the fold of mucous membrane 
termed the hymen, which lies within the entrance of the vagina 
in the female and more or less completely closes it, is by no means 
clear. The only thing that can be stated with certainty is that 
it is coincident in disposition with the elevation of the urethral 
mucous membrane of the male known as the colliculus seminalis. 

[It is an interesting fact that a similar and complete fold is present within 
the base of the oviduct in the virgin state of the lower Fishes (Sharks and 
Rays).] 

The Cloaca 

At a certain stage in the development of Man the urinogenital 
ducts and intestine open posteriorly into a common chamber, the 



THE URINOGENITAL SYSTEM 195 

cloaca. This points back to a condition which must have 
existed in the remote ancestors of Man, for a cloaca persists 
throughout life in Amphibians, Eeptiles, and Birds, as well as in 
the lowest Mammals, which last are on this account called the 
Monotremata. 

In the further course of development the cavity of the cloaca 
becomes divided into two, the posterior chamber serving as a 
prolongation of the rectum, the anterior forming a sinus 
urinogenitalis, from the anterior wall of which the genital 
eminence is developed (cf. Fig. 103, G and H). 



External Genital Organs of the Female 

Concerning the external genital apparatus of the female, the 
labia majora are probably to be regarded as partially developed 
homologues of the scrotum of the male. Indications of them are 
found even in the Lemuroidea and the Apes ; but in most Apes it 
appears that only the lesser system of folds found in women, the 
labia minora, form the boundary of the genital aperture. The 
labia minora, which form a strong praeputium and frenulum 
clitoridis, belong ontogenetically to the genital eminence, and are 
developed upon its lower surface. They thus fall under a 
different morphological category from the labia majora. 

The clitoris in Apes is both relatively and absolutely larger 
than in human beings, and its under surface is furrowed as far as 
the urinary aperture. This primitive condition is recalled by the 
occasional condition, due to arrested development of the genital 
eminence, known as hypospadias. 

In certain branches of the Ethiopian race the females are 
distinguished by a very slight development of the labia majora 
and of the mons veneris, and of hair about these parts. On the 
other hand, among the female Hottentots, a marked hypertrophy 
of the labia minora and of the prseputiimi clitoridis is well 
known, giving rise to what is known among Bushwomen as the 
" Hottentot apron." [This, however, is most probably due to 
manipulation, and to the wearing of a split stick with a weight 
attached.] The vagina appears (as in Apes) smoother, it being 
less strongly folded than in unmarried Europeans. In Japanese 
women the labia majora and the mons veneris are feebly developed 
and but little hairy, and the labia minora seem also to be but 
slightly developed (Bischoff). 



196 THE STRUCTURE OF MAN 

Male Genital Glands (Descensus Testiculokum) 

Among Mammals the genital glands of the male (testes) 
agree in their place of origin with those of the female (ovaries). 
Both are developed out of the germinal epithelium, differentiated 
near the dorsal wall of the coelom to the right and left of the 
vertebral colimin. But while, during further development, the 
ovaries, as a rule, shift down towards the pelvis, the testes may 
wander still farther {descensus testiculorum). This descensus is 
closely connected not only with the history of the testis, as the 
result of interaction between the organ and the parts immedi- 
ately surrounding it, but also with the relations of the testis to 
other organs more or less remote from it. 

Many variations occur among Mammals in the manner of 
descent of the testis, and in the changes in the ventral body wall 
which accompany it. It seems possible, however, as Klaatsch 
has shown, to reduce these variations to a simple ground plan. 
The descent of the testes, which is a new development peculiar 
to Mammals, is effected in its most primitive manner in 
Insectivores and Eodents; and everything points to the fact 
that it was originally a periodic phenomenon occurring in the 
adult. For instance, in the Hedgehog the testes retain their ori- 
ginal intra-abdominal position up to the rutting period ; but as 
that period approaches they come to lie in evaginable portions of 
the inguinal body wall. After the rutting season they always 
return into the abdominal cavity, but the mechanism by which 
this is accomplished is not yet clearly understood. 

In connection with the shifting of the testis, a structure 
termed by Klaatsch the "conus inguinalis" is of the greatest 
significance. This organ is best developed in the Muridse, and 
consists of a conical invagination of the muscular abdominal wall, 
at first connected not with the three lateral abdominal muscles, 
but only with the obliquus internus and transversus. Its 
internally projecting point, or at least its surrounding tissue, fuses 
with a cord-like structure called by Klaatsch the ligamentum 
inguinale (cf. Fig. 105). This ligamentum inguinale (which 
must not be confused with the gubernaculum or round ligament 
of earlier writers) is a subperitoneal strand containing smooth 
muscle, which arises, in both sexes, on each side of the genital 
ducts, and runs to the inguinal region of the abdominal wall, i.e. 
to that point which corresponds with the aperture of the canalis 
inguinalis interna. This " ligament," for which a parallel exists 



THE UEINOGENITAL SYSTEM 197 

in other differentiations of the ecelomie musctUature {e.g, the 
iniiseulua suspensorius duodeni, musculature, of the genital ducts), 
leaves the genital duct at the point where the ligamentum testis 
or ovarii reaches it. This coincidence of position by no 
means always obtains ; but the fact that it may do so has led to 
the erroneous idea that the ligaments of the genital ducts hitherto 
known as the ligamentum rotundum and the gubernaculum always 
and alone connect the ovary and testis with the inguinal 
region. The study of Ontogeny proves that in origin they are 
distinct from the ligamentum' inguinale. The latter, in the 
female, becomes the ligamentum rotundum uteri. Besides this. 




FlO. 105. — A, A FABTLY DlAQHiUMATiC REPBBSESTiTION OF TUB EmBBTOBIC UFPJO- 
A MlLB MaMUAL, SnOWINO ITS REUTIONS TO THE VeKTRU. 

Abdominal Wall. 
B, The PEsia and Sceotuu of a Human Ehbbto IE ck. lomg, with the Abejb 
Scroti (o.s,) mbbtino in the Middle Link. 

(Both fwubbs founded on the wobk of Klaatsch.) 

at., intestine; re'., snprarenal bod v ; re'., kidney; Is., snspensory ligament of tertU ; 
g.g,, testia ; d.g., genital duct f l.i., ligHmentum inguinale ; pr., processus vaginalia ; 
c.i,, conns inguindlis ; U., urinaiy bladder. 

the ligamentum inguinale, as well as the conns inguinaUa of 
Klaatsch, were called gubernaculum testis by former authors; 
in fact, the term gubernaculum was originally applied to the most 
heterogeneous structures. 

In the Insectivora and Kodents, the descent of the testis is 
accompanied by an evagination of the conus due to muscular 
contraction, so that the ligament may in this case rightly be 
termed a " gubernaculum." This evagination gives rise to a 
more or less marked bulging of the integument, to form the 
" bursa inguinalis " of Klaatsch. This pouch, which represents 
the point of least resistance in the abdominal wall, is composed 
of (1) the evaginated abdominal integument (scrotum, sac of the 



198 THE STRUCTURE OF MAN 

testis), (2) evaginated derivatives of the internal oblique and 
transversus muscles (cremaster), and its cavity is connected with 
the coelom hj a special canal (canalis vaginalis in the male, 
canalis Nuckii in the female). 

The differentiation of these parts, which was in all probability 
originally effected only in the adult, in some cases takes place at 
an earlier (Mouse) or even embryonic period (Squirrel). 

It is conceivable that next in order to the type represented 
by Eodents and Insectivores, there may have existed forms 
in which the descensus occurred periodically in youth, but in 
which, in more advanced age, in consequence of the loss of the 
reditus testium at the rutting season, it became fixed. Such 
forms are not actually known ; but the hypothetical stage is very 
nearly realised in Man, as in him, by the partial reinvagination 
of the bursa, and by the consequent formation of a conus 
inguinalis, we are still reminded, ontogenetically, of the periodical 
descensus and reditus testium, although it is but a very feeble 
process. There is thus reason for thinking that, among the 
Prosimii and Primates, forms corresponding with this hypotheti- 
cal stage might be found. 

The definitive descensus is due to a further evagination 
of the conus. The bursa inguinalis, however, which was once 
(as in the Eodents and Insectivora) the direct product of this 
very shifting of the testis, in Man first arises independently at 
some distance from it, farming what is known as the genital 
ridge or the outer genital fold. 

Among the lower Mammals the development of a permanent 
scrotimi has become established in the Marsupialia, Ungulata, and 
Carnivora. Among the Edentata only the Orycteropodidae 
possess a testis sac into which the testes periodically enter. In 
DasypuSy Bradypus, and Myrmecojphaga the testes are abdominal ; 
in Manis they are subintegumental, and lie in the inguinal region. 
In the Monotremes a descensus testiculi is not known to occur. 

In considering the phylogenetic origin of the descensus testiculorum, 
Klaatsch has formulated the following ingenious argument : — The mammary 
organ, which in the form of a somewhat circular patch of the integument, 
characterised by glands and smooth musculature, first became differenti- 
ated in the inguinal region, exercised a great influence on the abdominal 
wall. He has suggested that among the ancestors of the Mammals there 
occurred, as he believes is shown by the Monotremata, a transference of the 
mammary organ from the female to the male ;^ and that this may have 

^ In other words, Klaatsch interprets as the bomologue of this Mammary area a 
circumscribed wrinkled portion of the integument, only scantily covered with hair. 



THE URINOGENITAL SYSTEM 199 

exercised a great influence on the lower portion of the abdominal walL This 
would appear to have involved the invagination of a more or less circum- 
scribed portion of the lateral abdominal muscles by the glandular apparatus 
(which in the Monotremata has already attained large proportions), leading 
up to the differentiation of a compressor of the mammary organ out of the 
transversus muscle. He further surmises that this, which represented a 
primitive conus inguinalis, was retained in the Marsupials to assist in the 
extra-uterine nourishment of the young, and that it disappeared in the 
Placentalia owing to the substitution of other methods of providing for the 
offspring. The invagination of the conus into the coelom must, like the 
maturation of the glandular complex, have occurred periodically. The male 
conus became related to the male genital gland, and the periodic displacement 
of the latter (towards the point of the least resistance) must thus be associ- 
ated with its great increase in size at the times of sexual activity. For 
the ovaries this last factor has not to be taken into account, as they do not 
undergo such great variations of size ; and further, their power of descent 
is greatly diminished in consequence of their position in relation to the 
Miillerian ducts. 

The essential, that is the first, cause of the descensus remains unexplained, 
and the origin of the ligamentum inguinale is still a complete enigma. On 
the other hand, its connection with the uterus, its periodical increase in size 
during pregnancy, and especially its near relation to the conus inguinalis, and 
thus to the mammary organ, make it very probable that it originally arose 
in the female, and was transferred to the male with the other parts belonging 
to the mammary organ. 



Suprarenal Bodies 

These organs are probably to be traced to a double origin, 
partly from the mesonephros and partly from the sympathetic 
nervous system. Their physiological significance is as little 
known as their primitive history, and it is not certain whether, 
so far as Man is concerned, they are phylogenetically in a pro- 
gressive or in a retrogressive condition. 

The latter assumption is the more probable when we consider 
their great development during embryonic life. On the other 
hand, their rich blood-supply indicates some important physio- 
logical function performed throughout life. 

which is to be found on the level of the scrotum in the young stage of all 
Mammals, including Man, and which at a later stage meets the corresponding area 
of the other side in the middle line. The numerous smooth muscles which 
constitute the tunica dartos appear to correspond with the smooth muscle layer 
of the glandular area in the Monotremata. In all Mammals the area scroti is 
distinguished by the fact that the hair grows on wart -like elevations which 
are closely crowded together — a peculiarity which gives the area a characteristic 
api)earance. The hairs are provided with very small sebaceous glands ; the coiled 
tubular glands are much larger, and open near hairs disposed singly. In Man 
the tubular glands are less conspicuous. 



CONSPECTUS OF THE OEGANS MENTIONED IN 
THE TEXT, AEEANGED ON THE BASIS OF 
THEIE PHYSIOLOGICAL CONDITION 

I. Organs showing Eetrogressive Characters 

A, Retrogressively modified^ the Organs still performing 

clearly recognisable Functions 

Certain muscles of the lower leg and foot. 

Adductor transversus of the foot. 

Opponens of the ball of the little toe. 

Serratus posticus superior and inferior. 

The flexors proper of the fingers. 

M. pyramidalis (when comparatively well developed as 
accessory to the rectus abdominis). 

M. levator palpebrae superioris. 

Intestinal coecum. 

Eighth sternal rib. 

The eleventh and twelfth ribs. 

Sternum. 

The fifth toes. 

The fibula. 

Olfactory lobe of the brain and (in part) the olfactory organ. 

The canines and upper lateral incisors ; the molars, in so far 
as there is a decrease in the number of their cusps. 

The pre-maxillary bone. 

B, Retrogressively modified, the Organs having "become wholly or 
in part functiordess, some appearing in the Embryo alone, 
others present during Life constantly or in^ohstantly. For 
the greater part Organs which may be rightly termed 
Vestigial, 

Os coccygis. Cauda humana. ^ ^-\ ^■ 

Superfluous embryonic notochord and associatefd i^omites. 



CONSPECTUS OF ORGANS MENTIONED IN THE TEXT 201 

Embryonic cervical, lumbar, and sacral ribs. "^^ 

The thirteenth rib of the adult. 

The seventh cervical rib in the adult. 

The interarticular cartilage of the sterno-clavicular joint 
(probable vestige of the episternal apparatus). 

Ossa supra-sternalia. "^^ "^ ^ ^ ^j^///^.>/ 

Certain centres of ossification in the manubriimi sterni. 

The branchial clefts (for the most part) and branchial ridges.--? >'/yr 

Processus styloideus ossis temporis, and the ligamentum 
stylo-hyoideum. 

Anterior cornua of the hjjgjd, for the greater part. 

Foramen coecum of the tongue./^ 

Processus gracilis of the malleus. 

Post-frontal bone (?)- ^' 6' ^'^ - ' ^ / 

Ossa interparietalia (and ? prseinterparietalia). 

Processus paramastoideus of exoccipital. 

Torus occipitalis. 

Processus frontalis of the temporal. 

Processus coracoideus [meta- and epi-coracoid bones]. 

Os centrale carpi. 

Processus supracondyloideus humeri. 

Trochanter tertius femoris. 

The phalanges of the fifth toe, and less conspicuously of the 
third and fourth toes. - '^ ^^\ 

Muscles of the pinna and the Musculus occipitalis. 

M. transversus nuchse. 

Facial muscles transformed into tendinous expansions. 

Mm. plantaris and palmaris longus, when completely 
tendinous. 

M. ischio femoralis.Nv 

The caudal muscles.*^' ' 

M. epitrochleo-anconseus. ( 

M. latissimo-condyloideus. 

M. transversus thoracis (triangularis sterni). 

M. palmaris brevis. 

The transition bundles between the trapezius and the sterno- 
cleido-mastoideus. 

M. levator claviculae. 

M. rectus thoracis. 

M. cremaster. 

The primitive hairy covering or lanugo. 

Vestiges of vibrissae. 



202 THE STRUCTURE OF MAN 

The vertex coccygeus, the foveola and glabella coccygea. 

Certam vortices of hair on the breast. 

Nipples in men. 

Supernumerary mammary glands in women. 

Alleged vestiges of mammary pouches [?] 

Supernumerary olfactory ridges. 

Jacobson's organ, and ductus naso-palatinus. 

Papilla palatina and foliata. 

Plica semilunaris of the eye. 

Vasa hyaloidse (Cloquet's canal) of the embryo — the choroidal 
fissure. 

Lachrymal glands, in part. 

The epicanthus. 

M. orbitalis. 

Certain varieties of the pinna of the ear. 

The filum terminale of the spinal cord. 

Glandula pinealis and parietal organ. 

The parieto-occipital fissure of the brain [doubtful]. 

The obex, ponticulus, ligula, taeniae medullares, and velum 
meduUare anterius and posterius, of the brain. 

The hypophysis cerebri (pituitary body). 

The dorsal roots and ganglia of the hypoglossus nerve. 

The rami recurrentes of certain cranial nerves. 

Certain elements of the brachial and lumbo-sacral plexuses. 

The coccygeal nerve. 

The glandula coccygea. 

Palatal ridges. 

The sublingua. 

The formation of rudimentary dental papillae before the 
sinking of the dental ridge. 

The wisdom teeth. " — 

The occurrence of a third praemolar (reversionary). 

The occurrence of a fourth molar (reversionary). 

The vestiges of a third dentition. ^^/ y^. ^, ^ 

The ciliated epitheliimi of the embryonic oesophagus. *"^ — 

Bursa sub- and praehyoidea (ductus thyroglossus). 

Musculi broncho-oesophagei. 

The appendix vermiformis. 

Ventricle of the larynx (Morgagni's pouch). 

Lobus subpericardiacus of the lung (reversionary). 

Certain valves of the veins. 

Certain structures of a vestigial nature in the heart. 



CONSPECTUS OF ORGANS MENTIONED IN THE TEXT 203 

Arteria sacralis media. 
Arteria ischiadica. 

Superficial plantar arterial arch of the foot. 
The vena cava superior sinistra. 
Venae cardinales posteriores, and ductus Cuvieri. 
Vestiges (in the female) of the mesonephric system, and (in 
the male) of the Mlillerian ducts. 

Conus inguinalis, and ligamentum inguinale. 
The area scroti. 

C, Modified under Change of Function, though this cannot in 

oil cases he proved 

Suprarenal bodies. 

Glandula thyroidea. 

Glandula thymus. 

Bursa pharyngea. 

Anterior lobe of the hypophysis cerebri (pituitary body). 

Carotid and coccygeal glands. 

D, Charojcters Indicative of Change of Position or Shifting 

Proximal shifting of the pelvic girdle, and, correlatively, 
the shortening of the lumbar region of the vertebral column 
(assimilation of the fifth lumbar vertebra by the sacrum). 

Distal shifting of the shoulder girdle. 

Abbreviation of the coelom. 

Proximal and distal abbreviation of the osseous thorax. 

Power of abduction in the embryo and at birth of the first 
metatarsal and great toe. 

Shifting of the eye from the lateral surface of the head to 
the anterior. 

Wandering of the lachrymal glands. 

[Variations in arrangement] of the platysma myoides muscle. 

[Variations in arrangement] of the sphincter colli. 

Shifting of the navel. 

Shifting of the heart, the stomach, and the thyroid and 
thymus glands. 

Descent of the genital glands (testes and ovaries). 

Shifting of certain muscles of the lower leg on to the 
dorsum and plantar surface of the foot. 

Torsion of the himierus, radius, and ulna. 



204 THE STRUCTURE OF MAN 

Disposition of the foot at a sharp angle to the leg. 

Secondary separation of the orbit from the fossa temporalis. 

Shifting of the lachrymal bone on to the surface of the face. 

The disposition of the palatine bones in relation to the 
palatal processus of the maxilla. 

The fusion of the nasal bones. 

The position of the pinna on the adult head. 

The ultimate positions of the ribs upon the vertebral column. 

(Widening of the thorax, as an accompaniment of an altera- 
tion in the positions of the organs within the thoracic cavity.) 



II. Organs showing Progressive Characters, i.e. tending 

TOWARDS MORE PERFECT ADAPTATION 

Higher differentiation and more subtle development of the 
muscles of the thumb — ^both of those which pass from the fore- 
arm along the volar and dorsal surfaces to the thumb, and of 
those of the ball of the thumb. 

Increase in physiological efficiency of the hand in general, 
especially of the flexors of the hand and of the fingers, the palmaris 
longus excepted. 

Increased development and strengthening of the arch of the 
foot, of the tarsus, heel, and great toe. 

Secondary lateral extension of the malleolus fibularis. 

The perfecting of the whole lower limbs for support and 
ambulation (in adaptation to the upright gait). 

Development of the iliac expansions in the female, with 
widening of the sacrum and of the aperture of the pelvis. 

Curvature of the lumbar vertebral column. 

Gluteal muscles and muscles of the calf (gastrocnemius and 
soleus). 

More subtle differentiation of the facial muscles proper (as 
opposed to the muscles of the pinna and of the scalp). 

The projectile nose. 

Certain nerve tracts in the brain and spinal cord. 

The occipital lobes of the brain (posterior cornua of lateral 
ventricle and calcar avis ?) 

Higher degree of development of the brain cortex (histological 
differentiation concomitant with increasing intelligence). 

The more subtle differentiation of the muscles of the larynx. 
Articulate speech. 



CONSPECTUS OF ORGANS MENTIONED IN THE TEXT 205 

On glancing through this summary, it will be seen that the 
arrangement of the subject matter is not altogether a natural 
one; indeed, in introducing it, I have only sought to give a 
classified survey of the contents of this book. 

Physiological considerations must determine the ultimate 
method of grouping the facts, especially because, as was pointed 
out in the introduction, the term vestigial is, as a rule, 
only applied to such organs as have lost their original physio- 
logical significance. Eetrogressive organs, on the contrary, are 
such as may still remain functional, though, as a rule, only to 
a limited extent. It has further been seen that both these 
conditions in the process of degeneration may be, in different 
individuals, realised in one and the same organ. The palmaris 
longus and plantaris muscles furnish a case in point ; for while 
these, and especially the former, are not infrequently so well 
developed that there can be no doubt of their being functional, 
cases occur in which one or the other of them has become quite 
transformed into tendinous tissue and really vestigial. And in 
yet other cases these muscles may altogether have disappeared. 
On this subject Osborn makes the following appropriate remark : — 
" Both in the muscular and skeletal systems we find organs so 
far on the down grade that they are mere pensioners of the body, 
drawing pay {i.e. nutrition) for past honourable services without 
performing any corresponding work — the plantaris and palmaris 
muscles for example." ^ 

Many similar examples might be given. Confining our 
attention to muscles alone, it may sufiice to recall the pyramidalis 
and certain muscles of the head. 

^ Cf. this author's Cartwright Lectures, Lect. I. "The Contemporary Evolution 
of Man," Medical Record, Feb. 20, 1892. 



LIST OF THE OEGANS AND TOPICS CONSIDEEED 
m THE TEXT, CLASSED ACCOEDING TO THE 
SYSTEMS TO WHICH THEY EELATE 



I. Integument and Integumental Organs 



(a) Homy Structures, 

Vibrissse (tactile hairs). 
Primitive hairy covering (lanugo). 
Converging hair vortices, ex. vertex 

coccygeus. 
Glabella and foveola coccygea. 
Pseudohypertrichosis. 
Hypertrichosis vera. 
Nails (the fifth claw-like). 



{h) Glands, 

Montgomery's glands. 

Mammary pouches. 

Mammarv line. 

Supernumerary mammary glands 
and nipples (polymasty, poly thely). 

Pectoral hair vortices (probably indi- 
cating the former position of super- 
numerary nipples). 



II. Skeletal System 



(a) Vertebral Column, 

Cauda humana. 

Os coccygis. 

Curvature of the lumbar portion of 

the spinal column. 
Forward shifting of the sacral portion 

of the spinal column (assimilation 

of the last lumbar vertebra). 
Numerical increase of the lumbar 

vertebrae. 
Outgrowth of the transverse process 

of the sixth cervical vertebra. 

(6) Thorax, 

Quadrupedal form of the thorax in 
the child, with greater dorso-sternal 
diameter. 

Disappearance of the lumbar ribs. 

Disappearance of the cervical ribs. 



Reappearance of cervical, lumbar, and 
sacral ribs formerly present. 

Variations in development of the 
upper and lower ribs. 

Former greater extension of the 
pleuroperitoneal cavity, both an- 
teriorly and posteriorly. 

The eighth sternal rib. 

Reduction of the sternal ribs to six. 

Reduction of the sternunL 

Vestiges of the episternal apparatus. 

(c) Skull, 

Post-frontal bone. 
Os interparietale. 
Os prseinterparietale. 
Processus paramastoideus. 
Torus occipitalis. 

Suppression of the parietal process of 
the alisphenoid. 



LIST OF ORGANS ACCORDING TO SYSTEMS 



207 



Fusion of nasal bones. 
Participation of the os lachrymale in 

the superficial facial skeleton. 
Variation of the os lachrymale. 
Downward prolongation of the nasal 

process of the frontal bone. 
Lower bridge to the nose. 
Ductus naso-palatinus. 
The pre -maxillary and maxillary 

bones. 
Ossa palatina, in relation to the 

palatine processes of the maxillae. 
Distinctness of the ossa palatina, and 

tlie spina nasalis posterior. 
Vestiges of the branchial skeleton 

(thyro-hyoid apparatus, ossicula 

auditus). 

(d) Skeleton of the Limbs. 

Processus coracoideus [epi- and meta- 
coracoid bonesj 

Extension of the basis scapulae. 

Great development (divergence) of the 
iliac expansions. 

Length of the forearm in the embryo 
and in the lower races of Man- 
kind. 

Perforation of the olecranon fossa. 



Processus supracondyloideus (entepi- 
condyloideus). 

Os centrale carpi 

Trochanter tertius femoris. 

Variations in the length of the lower 
leg. 

Platyknemia. 

Exclusion of the fibula from articula- 
tion with the femur. 

Marked convexity of the condylus 
extemus tibiae. 

Great development of the malleolus 
tibialis in the embryo, the lower 
races of Mankind, and Anthro- 
poids. 

Predominance of the great toe. 

Great development of the tarsal 
elements. 

Parallel disposition of the great toe 
with the others, in the adult. 

The great toe in the embryo and the 
lower races. 

Reduction of the fifth (or fourth and 
fifth) toes (fusion of their terminal 
and penultimate phalanges). 

Comparison of the position of the 
limbs in the human embryo and 
the lower Vertebrates. 



Ill Muscular System 



M. serratus posticus superior et 
inferior. 

Mm. caudae humanae. 

Traces of metamerism in the ab- 
dominal muscles. 

M. rectus abdominis. 

M. pyraraidalis. 

Mm. scaleni. 

M. triangularis stemi. 

M. cleido-occipitalis. 

M. subcutaneus colli (platysma 
myoides). 

Mimetic muscles. 

M. sphincter colli. 

M. transversus nuchae. 

M. epicranius. 

Muscles of the pinna. 

M. palmaris longus. 



M. plantaris. 

M. flexor sublimis digitorum. 

M. flexor profundus digitorum. 

M. flexor brevis digitorum pedis. 

M. extensor brevis digitorum pedis. 

Mm. interossei pedia 

M. adductor hallucis. 

M. opponens minimi digiti. 

M. latissimo-condyloideus. 

M. sternalis. 

M. epitrochleo-anconaDus. 

M. levator claviculae. 

M. ischio-femoralis. 

Muscles of the thumb (especially the 

flexor longus pollicis). 
Mm. glutei (esp. gluteus maximus). 
M. gemellus superior. 
,Mm. soleus and gastrocnemius. 



208 



THE STRUCTURE OF MAN 



IV. Nervous System 

(a) Central Nervous System 



Filum terminale. 

Glandula coccygea. 

Pyramidal tracts. 

Parieto - occipital fissure ("Affens- 

palte"). 
Pineal gland (epiphysis cerebri). 

Pituitary body (hypophysis cerebri). 



Lobus olfactorius. 

Roof of the fourth ventricle. 

Obex, ligula, vela meduUaria, taeniae 

medullares. 
Occipital lobe of cerebrum. 
Posterior cornu of lateral ventricle. 
Calcar avis. 



(6) Peripheral Nervous System 

Roots and ganglia of hypoglossus. Traces of tegumental sense organs in 

Rami recurrentes of certain cerebral foetal life. 

nerves. Variations in the brachial and lumbo- 

^cral plexuses. 



V. Sense Organs 



Disappearance of an olfactory ridge 

in the embryo. 
Papilla palatina and foliata. 
Jacobson's organ. 
Vasa hyaloidea (Cloquet's canal). 
The projectile nose. 
Orbitalis muscle. 



Levator palpebrse superioris muscle. 

Plica semilunaris. 

Supernumerary lachrymal glands. 

Epicanthus. 

Auditory ossicles (relations to the 

visceral skeletal arches). 
The middle ear (hyoid visceral cleft). 



VI. Alimentary System 



Palatal ridges. 

Milk dentition. 

Indications of a third dentition. 

Wisdom teeth. / 

Possible indications of free dental 

papillae before the down-growth of 

the dental ridge. 
Canine teeth. 
Outer upper incisors. 
Cheek teeth (reduction of cusps and 

fangs). 
Appearance of a third premolar and 

a fourth molar. 
Sublingua. 



Glandula thyroidea. 

Glandula thymus. 

Foramen coecum and base of the 

tongue. 
Ductus thyroglossus. 
Bursae supra- and praehyoidea. 
Carotid gland. 
Bursa pharyngea. 
Constriction of the stomach. 
Ciliated epithelium in the oesophagus. 
Diverticulum ilei. 
Coecum. 
Vermiform appendix. 



VII. Eespiratory System 

Metamorphosis of the aortic arch Sinus Morgagni (laryngeal resonant 

system. chamber). 

Branchial pouches and cervical fistulae. Sinus and Lobus subpericardiacus. 



LIST OF ORGANS ACCORDING TO SYSTEMS 



209 



VIII. Circulatory System 



Vestiges of valves in the embryonic 

heart. 
Vestiges of the sinus venosus, in the 

heart. 
Intestinal arteries. 
Arteria sacralis media. 
Arteria ischiadica (genesis of femoral 

artery). 
Superficial vascular arch of the foot. 
Cardinal veins. 



Ductus Cuvieri. 

Sinus venosus cordis. 

Persistence of the post, cardinal veins 
in the form of a double vena cava^ 
inferior. 

Metamorphosis of superior caval 
veins. 

Valves of the intercostal and intes- 
tinal veins. 



IX. Urinogenital System 



Pronephros and mesonephros. 
Vestiges of the mesonephros. 
Uterus duplex, bipartitus, bicornis, 

and simplex. 
Hypospadias. 



Descensus or reditus testiculi. 
Conns inguinalis. 
Ligamentum inguinale. 
Area scroti. 
Suprarenal bodies. 



SOME OEGANS AND VESTIGES OF OEGANS, AVHICH 
SHOW [STEUCTUEAL COMMUNITY WITH] VEEY 
PEIMITIVE VEETEBEATE TYPES 

Conditions DEnNixivE in Fishes (Elasmobranchs) are 

INDICATED BY 

(1) The free dental papillae projecting above the surface of 
the mucous membrane before the sinking of the dental ridge. 

(The appearance ontogenetically of the dental ridges, long 
before the first osseous rudiments, points back to the 
extremely early phylogenetic appearance of teeth, in 
Vertebrates, before any of the other hard structures of 
the body.) 

(2) The pineal gland and pineal organ (a parietal foramen 
in the roof of the skull is found in Fishes as early as the 
Devonian period, and the organ occurs in the Marsipobranchii). 

(3) The pituitary body (hypophysis cerebri). 

(4) The branchial pouches. 

(5) The vessels of the visceral arch system. 

(6) The vasa hyaloidea of the vitreous body (Cloquet's 
canal). 

(7) The cardinal veins. 

(8) Certain structures, appearing in the development of the 
heart, vestiges of which are found in the fully developed organ. 

(9) The arteria caudalis (A. sacralis media). 

(10) The pro- and meso-nephric excretory apparatus. 

(11) The possible vestiges of a third set of teeth (pointing 
back to a probable successive renewal of teeth, such as 
characterises Fishes, Amphibians, and Eeptiles). 



INDICATIONS OF DEFINITIVE CONDITIONS 211 

Conditions DEnNixivE in Amphibia and Eeptiles are 

INDICATED BY 

(1) The arteria ischiadica [cruralis]. 

(2) The double rectus abdominis muscle. 

(3) The foramen supracondyloideum (entepicondyloideum) 
humeri (found in Amphibians and Eeptiles as early as the 
Permian period). 

(4) The presence of (supernumerary^) lachrymal glands below 
the eye. 



CONCLUDING EEMAEKS 

In the course of Phylogeny the body of Man has undergone a 
series of modifications which still in part find expression in his 
Ontogeny. There are indications that changes in his organisa- 
tion are still continuing, and that the Man of the future will be 
different from the Man of to-day. It is the more necessary to 
emphasise this, because it has only recently been asserted by one 
in authority in the anthropological world, that "since the Neolithic 
Age Man has been a fixed type." 

I willingly admit that nothing is gained by the mere 
demonstration of "animal likenesses," and that the final and 
only satisfactory solution of the great riddle of Man must lie in 
the demonstration of his genealogy and the line of his inheritance. 

Although small and insignificant in their first appearance, 
structural changes become more and more distinctly marked 
from generation to generation, and more and more definitely 
fixed according to the laws of heredity and selection. There 
exist different degrees of the degenerative process : first an 
organ begins to degenerate in the adult body, then this 
degeneration finds expression in the embryo, then the organ 
in question only occurs in a certain percentage of the in- 
dividuals as a reversion, and finally even such occasional 
occurrence ceases, and all trace of the organ is lost. Osborn 
calls this process of gradual extinction the "long struggle 
of the destructive power of degeneration." 

Although these changes are so manifold and follow such 
different directions (take, for example, those of the musculature), 
one principle lies at the bottom of them all, viz. the endeavour 
to shake off, as far as possible, all that is unnecessary and 
superfluous, in order to make room for further development. 
Weismann very justly remarks : " If Nature were not able to 
effect the disappearance of superfluous organs the transformation 
of species would have been well-nigh impossible, for the existing 



CONCLUDING REMARKS 213 

parts which had become superfluous would have been in the way 
of other active parts, and would have hindered their development. 
Indeed, had all parts which the ancestors possessed been necessarily 
retained, an abnormal animal would at last have been produced — 
a monster no longer capable of living. The degeneration of 
parts which have become superfluous is thus a condition of 
progress." 

But what is it that actually initiates these various changes ? 
What is their first cause ? This question cannot be answered ofl"- 
hand on account of the great number of circumstances which 
have to be taken into account. First, we have to consider 
external influences of the most varied kinds which affect the 
diflerent organs, or systems of organs, in a progressive or 
retrogressive manner, leading to new acquisitions or to gradual 
losses. These changes, however, have, as it were, to be intro- 
duced by the occurrence of slight variations, and then (if I may 
use a military term) when once a breach has been made in any 
part, a point of least resistance is formed for pathological affec- 
tions, as I have tried to prove in the foregoing pages, and a 
substitute for the gradually degenerating organs has to be found. 
In other words, as soon as a transformation takes place in any 
part of the body, correlative alterations in some other part 
commence, so that, as it were, a wave of modification passes from 
one system of organs to another. For example, when the 
dentition of our ancestors degenerated, and the canines became 
reduced, the important weapons of attack and defence thus lost 
had to be replaced, if the struggle for existence was to be 
advantageously maintained. Concurrently with the reduction of 
powerful jaws the brain was developing, and the intelligence 
attained a sufficiently high degree of perfection to invent 
weapons, at first no doubt of a very simple character. Or 
again, as the foot gradually changed from a seizing organ into 
one for support of the body, and its musculature consequently 
changed, then, in adaptation to the new function, great 
alterations had to be eflected not only in the skeleton of the 
limb, but also in its muscular and nervous system, e.g, the 
muscles of the calf and buttocks attained a massive development. 
Such examples might be multiplied, but the above will suffice 
to show that these modifications are not mere freaks of chance, 
mere lusus naturae, but are the expression of law - abiding 
processes, even if we cannot always succeed in determining their 
first cause. At all events, these processes need immense periods 



214 THE STRUCTURE OF MAN 

of time for their accomplishment, so that, as a rule, they are 
removed from direct perception by means of the senses, and can 
only be inferred from the evidence of Phylogeny, Comparative 
Anatomy, and Ontogeny. 

This applies not only to Man, but to the whole animal 
kingdom, which yields us a long series of examples of degenera- 
tion. Here also we find evidence of the great importance of the 
external conditions of life to which the organism responds. One 
of the most striking proofs of this is afforded by the degenerate 
condition,' or even entire absence, of eyes in animals living in 
the depth of the ocean or in caves. Such animals also illustrate 
how the loss of one organ is compensated for by the increased 
development of other organs. From the same point of view are 
to be considered the limbless Amphibia, and the Slow-worms, 
and another group of Eeptiles of essentially similar adaptive 
organisation, the Amphisbsenidae, and finally the more familiar 
Earthworm itself. 

Whereas, among the above-mentioned cases, it is the organ 
of sight which atrophies ; in other animals, the olfactory organ 
disappears, and I may especially refer to those Fishes known, 
from the characters of their jaws and teeth, as the Plectognathi 
Gymnodontes. Here,^ in adaptation to a diet of Crustacea and 
Molluscs which are very difficult to crush, the musculature of the 
jaws develops to an extraordinary degree, displacing the olfactory 
apparatus to such an extent that the olfactory nerve is reduced 
to a minute thread, which branches either within a mere tegu- 
mental olfactory process or simply under the surface integument 
of the olfactory region. 

Until quite recently, the question wherein lay the cause of 
the degeneration of an organ was thought to be satisfactorily 
answered as follows : the organ is not used, and the degenerating 
effect of disuse, passed on from one generation to another, gains 
in intensity, until it leads to the total removal of the organ in 
question. This answer presupposes what is often stated, but has 
never been proved, viz. the inheritance of acquired characteristics} 

^ Cf. Wiedersheim, ^^ Das Geruchsorgan der Tetrodonten." KoUiker Gratula- 
tionsschriftf 1887. 

2 [This statement requires qualification. It is true that we have no very satisfac- 
tory concrete instance of a chance structural modification of an individual having been 
transmitted by inheritance to its own immediate offspring. But, on the other hand, 
as Herbert Spencer has argued with great force, there seems no way of explaining 
the phenomena of highly organised life, except on the supposition of some transmis- 
sion of characters acquired in adaptation to the environment.] 



CONCLUDING REMARKS 215 

Weismann has recently conclusively proved that this answer is 
not sufficient, and that it must first of all be shown how it can 
come to pass that a portion of the body which up to a certain 
time is indispensable to existence, should disappear as soon as it 
is not needed. The real cause, according to Weismann, lies in 
a converse process, that is, the cessation of Natural Selection — 
in Panmixia (general cross-breeding). In other words, as soon 
as, by change in its external surroundings, an organ is excluded, 
its condition becomes retrogressive. Then the general inter- 
breeding between individuals in which the organ in question is 
well developed and others in which it is but feebly developed, 
which latter have survived in spite of this, leads to its slow but . 
steady degeneration.^ 

The numerous above-mentioned cases of degeneration in the 
organs of the human body should also, without doubt, be regarded 
from this point of view. The fact that the degree of development 
of this or that organ {e.g. the sense organs, which are incompar- 
ably more highly developed in savages than in civilised men) is 
no longer of supreme importance to the individual, i.e. no longer 
necessary for his prosperity, leads to a degeneration, which, in the 
struggle for existence, could only be compensated for by a high 
degree of civilisation. Weismann gives the following striking 
example of this : " We can at the present day earn our bread 
quite independently of the acuteness of our hearing and the 
delicacy of our scent, indeed, even the sharpness of our sight is no 
longer a decisive factor in our success in the struggle for existence. 
Since the invention of spectacles, short-sighted men suffer hardly 
any disadvantage as compared with the long-sighted in their 
capacity for earning a living, at any rate in the higher circles of 
society. This is why so many short-sighted people are to be 
found among us. In ancient times a short-sighted soldier, or 
still more a short-sighted general, would have been simply an 
impossibility, as would also a short-sighted huntsman ; indeed, 
in nearly all branches of human society short sight would have 
been a considerable obstacle, and would have rendered it difficult 
or impossible for a man to thrive and prosper. This is now no 
longer the case ; the short-sighted man can make his way like 

^ [This argument is unsatisfactory. Panmixia alone could not lead to the dis- 
appearance of any organ. Natural selection may effect an increase in an organ, by 
eliminating those below a certain average ; or the diminution of a structure, by 
eliminating all above a certain average. But it is not easy to see how Panmixia, or 
the cessation of Natural Selection, could alter the average in any way. ] 



216 THE STRUCTURE OF MAN 

every other, and his short sight, so far as it involves hereditary 
tendency, will be handed on by him and will help to make 
hereditary shortness of sight a widely-spread characteristic in 
certain classes of society." 

The above sufl&ciently illustrates the fact that progressive 
variations are closely connected with retrogressive variations, 
indeed that to a great extent the former are rendered possible 
by the latter. If it be true that the adaptation of a creature 
to its surroundings depends on the process of Natural Selection, 
we must also consider that Natural Selection is the determining 
factor in both retrogressive and progressive processes. We have, 
then, to fall back on the general law of Selection propounded 
by Charles Darwin, which may be summed up as follows : survival 
only of the fittest, transmissibility by inheritance, and the gradual 
improvement of what is advantageous from generation to genera- 
tion, till the highest possible degree of perfection is reached. 

But wherein lies Man's special " perfection " ? Does such 
perfection exist, and if so, is it, in comparison with other living 
beings, as universal as is generally assumed ? Let us look at 
this matter a little closer. 

/ There would appear to have been a time when our ancestors 
< were protected against the inclemencies of the weather by a 
natural covering of hair, and against insects and other injurious 
influences by an extensive tegumental musculature, when the 
pinna of the ear, more advantageously disposed than at present, 
and moved by numerous and powerful muscles, collected the sounds 
of approaching danger incomparably better than at the present 
day, and when the sense of smell, probably intensified by Jacobson's 
organ, was more highly developed than now. Indeed, at a 
very low stage of phylogenetic development, when the visual organs 
were placed laterally on the head, and were furnished with a 
third eyelid, and regulated by more numerous muscles, there may 
even have been a " third eye " which could perceive what took 
place above the head (c£ the pineal organ, p. 133). The intestinal 
tube may have been longer, and thus better suited than at the 
present day for vegetable diet, the ancestor of Man enjoying at 
any rate more favourable conditions of existence as a vegetarian 
than his successor now does (compare also the former greater 
number of cheek teeth). He may also have had the further advan- 
tage of not possessing a vermiform process of the coecum which 
predisposes to disease, and causes the destruction of a consider- 
able percentage of his fellows. 



COXCLrDESG REMARKS 217 

The herbiTorous stage was followed by an omnivorous one, 
characterised bjr the development of powerful canines. In this 
way, as skill in hunting and slaying animals de\'eloped, and 
carnivorous diet became of continually greater importance, the 
intestinal tube would appeair to have begun to shorten and the 
processus vermifonnis to become constricted. 

Laryngeal sinuses may have been developed, which, acting as 
resonators, lent the voice greater strength and carried it farther, 
and thus made it a means of frightening or enticing. The 
lower jaw, the neck and its musculature, were far more powerfully 
developed than now. 

In the male the genital glands mav have remained, as thev 
now normallv do in the female, within the abdominal cavitv, 
and been thus better protected from injury than at present. At 
a later stage even, when they had changed their position, and had 
reached the pouch-like appendages of the abdominal integument, 
they could still be withdrawn into the ca\nmi abdominis, at least 
temporarily, by means of a well-developed muscle (cremaster). 
This is still indicated by ontogenetic processes. 

There can be no doubt that the ancestors of Man were pro- 
vided with a more extensive mammary system and more numerous 
mammae than he to-day possesses, and the significance of this fact 
is equally clear. It can only be explained by the assumption that 
a greater number of young were originally produced at a birth. 
This, of course, was of advantage in the preservation of the species. 

It follows from the above that in the course of a long 
geological period, Man has gradually lost a great number of 
advantages once possessed by his ancestors, and the question 
arises whether he has acquired any others in exchange for those 
lost. This certainly is the case, and this indeed must have 
been so, otherwise the species Homo would have failed in the 
struggle for existence. We thus have a series of exchanges, based 
(if we take only the most important organ into consideration) 
upon the unlimited capacity of development of the human brain. 
This one acquisition, supported by an increased functional 
efficiency of the hand and by the development of articulate speech, 
has entirely compensated for the loss of the great series of ad- 
vantageous arrangements mentioned above. They had to be 
sacrificed in order that the brain might successfully develop, and 
that the Homo sapiens of to-day, with his surprising adaptability 
to the most varied conditions of life, might be produced. 

This momentous exchange took place slowly and only after 



218 THE STRUCTURE OF MAN 

great opposition. It was not accomplished without a struggle, in 
which every inch of the already occupied territory had to be 
painfully fought for ; and the extraordinary tenacity with which 
certain favourable positions once attained are clung to, is seen in 
the fact that some of them are still taken up by the organism 
as dim reminiscences of the past, perhaps only during foetal life. 
These ancient ancestral pictures, — for such indeed they are — are 
eloquent witnesses of a time long since past. They keep our 
vision clear, when we have, as in this present case, to be impartial 
judges of ourselves. 

As Testut appropriately says : Let us not unjustly reproach 
anatomists with lowering Man, with drawing him down from his 
high position : it is true that Anatomy does rank Man in the 
class of the Mammalia, but it places him in the highest order 
of that class, that of the Primates; and although it cannot 
entirely separate him from these, it gives him the highest possible 
position among them. Anatomy not only makes Man the most 
perfect of Primates, but also proclaims him first of the foremost 
of all living beings.^ As Broca has said : " That may well suffice 
for his ambition and his glory." I cannot do better than 
conclude with the following words of the last-named author, which 
are no less worthy of consideration \—/' Pride, which is one of the 
most characteristic traits of our nature, has in many minds 
prevailed over the calm testimony of reason. Like those Eoman 
Emperors who, intoxicated with their universal power, ended by 
denying their manhood, and by believing themselves to be 
demigods, so the king of our planet pleases himself with the 
thought that the nature of the vile animal which is subject to 
his caprices cannot have anything in common with his own. 
The proximity of the monkey is to him inconvenient ; he is no 
longer satisfied to be the king of animals, he desires that an 
immense unfathomable abyss should separate him from his 
subjects ; and, sometimes, turning his back on the earth, he takes 
refuge, with his endangered majesty, in the nebulous sphere of the 
Eeign of Man. But Anatomy, like that slave who followed the 
triumphal car, repeating the words ' Memento te hominem esse,' 
comes to agitate him in this self-admiration, and reminds him 
that reality, visible and tangible, links him with the animals."^ 

^ [Cf., however, Minot, *'Is Man the Highest Animal"? — Froc. Americ, Assoc. 
f(yr the Advancement of Science, 1881, p. 240.] • 



GLOSSAEY OF TECHNICAL ZOOLOGICAL TEEMS 

OCCUEEING IN THE TEXT. 

Amblystoma. — A Tailed Amphibian of the United States and Mexico, t ^ 

A3IM0C(ETES. — The sexually immature larva of the Lamprey. 

Amniota. — The three higher classes of Vertebrates, i.e. Reptiles, Birds, and 
Mammals, the embryos of which are enveloped in an amnion. 

Amphioxus. The Lancelet. — [The lowest animal possessing, in the adult 
state, a vertebral skeleton (notochord).] 

Amphisb-enid^ — Lizards with Snake-like bodies, which live underground. 

Anamnia. — The two lowest classes of Vertebrates, i.e. Fishes and Amphi- 
bians, the embryos of which are not enveloped in an amnion (ef. Amniota). 

[Anatomy. — The study of gross structure.] 

Anthropoids, also Anthropomorpha. — The highest "man-like" Apes 
(Gibbons, Orangs, Gorillas, and Chimpanzees). 

Anura. — Tailless Amphibians (Frogs and Toads). 

Aplacentalia {Mammalia aplacentalia). — The lowest Mammals, i.e. the 
Ornithodelphia (Monotremata) and the Marsupialia. The Monotremata 
are oviparous. The Marsupials produce immature young, which are in 
most of them carried about after birth in a pouch (marsupium) formed 
by the abdominal integument. [In neither Monotremata nor Marsupials 
is an allantoic placenta developed like that of all the higher Mammals 
(Placentalia).] 

Arctomys marmotta. — Marmots ; [terrestrial Rodents inhabiting Europe, 
North Asia, and North America.] 

[Atavism. — The reversion to the condition of a lower type.] 

Ateles. — The Spider Monkey of South America. 

AuCHENiA. — The Llama. 

[Biology. — In English, the study of all phenomena manifested by living 

organisms. 1] 
Bo VINA. — Oxen. 

Bradypus. — A South American Sloth. 
Branchiosaurus. — A Tailed Amphibian of the Permian period. 

Capromys. — Arboreal Rat-like animals found in Cuba and Jamaica. 
Carnivora. — Beasts of prey (flesh-eaters). Especially Felidse and Canidae. 
Cavia. — The Guinea-Pig. 
Cebus. — The " Capuchin," a leading genus of American Monkeys. 

^ [The term " Biologic " of continental observers is usually applied to the study 
of life itself, i.e. it is more nearly equivalent to our English term Physiology.] 



220 THE STRUCTURE OF MAN 

Cercopithecus. — A family of African Apes — [the "Green Monkeys" of 
menageries]. 

Cervus capreolus. — The Roebuck. 

Cetacea. — An order of Aquatic Mammals (Whales, Dolphins, and Porpoises). 

Chelonia. — Turtles and Tortoises. 

[Chimpanzees. — Anthropoid Apes, readily remarkable for the relative short- 
ness of the fore-limb. Confined to West and Central Equatorial Africa.] 

Chiroptera. — Bats. 

Cholcepus. — The two-toed Sloth of Northern South America. 

Ccelogenys. — The " Paca," a large Rodent somewhat resembling the Guinea- 
Pig, inhabiting Central and South America. 

Dasyprocta. — The " Agouti," a near relative of the Ccelogenys. 

Dasypus. — One of the Armadillos. 

Delphinus. — The common Dolphin. 

DicoTYLES. — The Peccary, or New World Pig. 

DiDELPHiA. — Marsupials, Mammalia having two vaginae. 

Dipnoi.— Fishes having not a few points of resemblance to the Amphibia. 

[Remarkable among fishes for the conversion of the air-bladder into a 

functional Jung] (confined to certain rivers of Queensland, Tropical 

Africa, and South America). 
Duckbill. — The "Platypus" of Australia, one of the Monotremata. (Cf. 

Aplacentalia and Ornithodelphia.) 

Echidna. — The " Spiny Ant- Eater " of Australia, one of the Monotremata. 

(Cf. Aplacentalia and Ornithodelphia.) 
Edentata. — An order of Mammals, comprising the Ant-Eaters, Armadillos, 

and Sloths. 
[Elasmobranchii. — The lowest living order of true Fishes, includes the Sharks, 

Rays, and Herring Kings, with their allies.] 
[Embryology. — The study of the earlier growth stages of living organisms, 

in the higher animals up to the completion of organ formation. A 

department of the wider study of Development] 
Erinaceds. — The Hedgehog. 

Ganoidei. — A group of living Fishes, [including the Sturgeons, the Bony 

Pikes of North America, and the Polypterus or ** Bichir " of the Nile, 

and their allies.] 
Gorillas. — [The largest of the Anthropoid Apes. Confined to West 

Equatorial Africa.] 
Gymnophiona. — Limbless Amphibians (Coecilians) with Snake-like bodies, 

some of which are known to live a subterranean life. 

Hatteria. — The "Tuatara" of New Zealand. A "Lizard" of very 

primitive structure. 
[Histology. — The study of the minute structure of tissues and organs.] 
HoM(E08AURUS. — A Fossil Lizard [of the Jurassic of the European Continent], 
Hylobates. — The Gibbons ["Long -armed Apes." Anthropoid Apes, con- 
fined to South-east Asia. The only Apes which habitually walk upright]. 
Hyperoodon. — A toothed Whale of the North Atlantic, sometimes called the 

" Bottlenose." 
Hystrix. — The Porcupine. 



GLOSSARY OF TECHNICAL ZOOLOGICAL TERMS 221 

Iiruus. — [A genus of Old World Apes, allied to the only Euroi)ean Ape — the 

Barbary Ape (Macacus) of Gibraltar.] 
Iksectivora. — [A heterogeneous order of Mammals, which includes the 

Hedgehogs, Shrews, and Moles.] 

Lkmuroidea. — Arboreal animals of the Old World, chiefly of Madagascar, 
with dentition approximate to that of certain Insectivora, and as a rule 
with Monkey- and Ape -like prehensile (cf. Tarsius) limbs. (The 
"Tarsier" and "Aye Aye" are of this sub-order.) 

Macacus. — (Cf. Inuus.) 

Manatee. — The " Sea Cow," an aquatic Mammal, famous for having given 

rise to the fable of the Mermaid. 
MANia — One of Scaly Ant-Eaters of the Old World. 
Mabsipobranchh. — The Lampreys and Hags. 
Mabsupialia. — A sub-class of Mammalia, the females of most of which are 

provided with a marsupium, or pouch, enclosing the teat-bearing area of 

the body-wall. (Cf. also Didelphia and Aplacentalia.) 
MoNODELPHiA. — Mammals possessed of a single vagina, i.e, all those above 

the Marsupials. 
MoNOTREMATA. — The lowest sub-class of Mammals. (Cf. Aplacentalia and 

Ornithodelphia.) 
[Morphology. — The study of form and arrangement of the parts of the 

body.] 
[MuRlDiE. — A family of Rodents, embracing the Rats and Mice.] 
MusTELiDiE. — A group of Carnivores, including the Weasels, Pole-Cats, and 

Martens. 
Mycetes. — The Howling Monkeys of South America. 
Myooale. — [The " Desman," an aquatic Insectivore, related to the Moles and 

Shrews, occurring in the Pyrenees and South-East Russia.] 
Myrmecophaga. — [One of the Hairy Ant-Eaters of South America.] (Cf. 

Edentata.) 

[Ontogeny. — The developmental history of the individual.] 

Orangs. — [Anthropoid Apes confined to the Oriental region. The " Red 

Haired Apes " of Sumatra and Borneo.] 
[Ornithodelphia. — The lowest living Mammals (Australian). Oviparous 

Mammals, having non-united oviducts and a cloaca. (Cf. Monotremata, 

Duckbill, and Echidna.)] 
Orycteropodid-«l — The " Aaardvark," or hairy Ant-Eaters of the Old World. 

(The Cape Ant-Eater.) 

Pal^ohatteria. — A fossil "Lizard" [of tlie Permian beds in Saxony] related 

to Hatteria. 
Petromyzon. — The Lamprey (cf. Ammocojtes and Marsipobranchii). 
Phalangista vulpina. — The Australian " Opossum," or " Vulpine 

Phalanger." A climbing Marsupial 
Phoca. — The Seal. 
PnoCiENA. — The Porpoise. 

Phyllomys. — An extinct Rodent, from the Brazilian caves. 
[Phylogeny. — The developmental history of the race.] 



222 THE STRUCTURE OF MAN 

[Phylum. — A term applied to any great race or assemblage of genetically 

related forms of life, which conform to the same fundamental type.] 
[Physiology. — The study of the functions of living matter, i.e, of the living 

in action.] 
PiNNiPEDiA. — Marine Camivora, having feet transformed into paddles. The 

Seals, Sea-lions, and Walruses. 
[Placentalia. — The highest sub-class of Mammals. Those Mammals which 

develop an allantoic placenta.] 
Primates. — The highest order of Placental Mammals, including the Lemur- 

oidea. Monkeys, Apes, and Man. 
Prosimii. — (Cf. Lemuroidea.) 

Reversion. — (Cf. Atavism.) 

R0DE2JTIA. — An order of gnawing Mammals (Rabbits, Rats, Porcupines, 
Squirrels, and their allies). 

Saurians. — Lizards. 

Selachians. — Sharks and Dog-fishes. (Cf. Elasmobranchii.) 

SiRENiA. — An order of Aquatic Mammals. (Cf. Manatee.) 

Slow Worms.— .-A group of Limbless Lizards. 

Stegocephala. — Fossil Amphibians, most abundantly represented in the 

Carboniferous, Permian, and Triassic strata. 
Stenops. — The " Slender Lori " of Ceylon, one of the Lemuroidea. 
Sus SCROFA. — The Domestic Pig. 

Tarsius. — [The "Tarsier" of Borneo, Sumatra, and the Celebes.] One of 

the Lemuroidea. 
Teleostel — The Bony Fishes. 

Tetrodonta. — Aberrant Bony Fishes, belonging to the family Gymnodontes. 
Toothed Whales. — A group of the Cetacea, including the Cachelots or 

Sperm Whales, Dolphins, and Porpoises. (Cf. Cetacea.) 

Ungulata. — The Hoofed Mammals. 

Urodela. — The Tailed Amphibians. Newts, Salamanders, and their allies. 

Ursus. — The Bear. 

ZiPHius. — [A long-snouted Toothed Whale met with in most of the great 

seas.] 



INDEX 



Acetabulum, 74 

Affenspalte, 127 

Ainos, 10 

Alimentary canal, 155 

Amasty, 22 

Ankle-joint, 84 

Aorta, 181' 

Areae scroti, 197, 199 

Arterial system, 181 

Arteries, intestinal, 184 
of fore-limb, 182 
of hind-limb, 183 

Artery, hyaloid, 147 
hypogastric, 181 
median sacral, 182 

Astragalus, 84 

Atriuin, 180 

Auditory organ, 150 

Bone, alisphenoid, 58 

coracoid, 71, 72 

cotyloid, 74 

epicoracoid, 72 

epipteric, 59 

frontal, 55, 61 

hyoid, 65 

interparietal, 55 

lachrymal, 60 

malar, 58 

metacoracoid, 72 

nasal, 60 

palatine, 63 

post-frontal, 55 

premaxillary, 61 

sphenoid, 58 
Bones, metatarsal, 88 

turbinal, 60, 141 

"Wormian, 60 



Brain, 127 

fissures of, 127 

growth of, 53 

olfactory lobe of, 137 

transitory fissures of, 138 

weight of, 51, 128 
Branchial arches, 66, 151 

pouches, 171 

skeleton, 172 
Breasts, supernumerary, 18 
Bronchus, eparterial, 176 
Bursa inguinalis, 197, 198 

pharyngea, 164 
Bursae prae- and supra-hyoid, 162 

CiECUM, 167 
Calcaneum,'84 
Canalis inguinalis, 196 
Canals, naso-palatine, 145, 156 

Nuckii, 198 

tubo-tympanicus, 151 

vaginalis, 198 
Carpus, 79 

Caruncula lachrymalis, 149 
Cauda humana {see Tail) 
Cerebellum, 131 
Cerebrum, lobes of, 131 
Cervical groove, 66 
Choanae, 61 
Chorda dorsalis, 49 
Circulatory system, 180 
Clavicle, 71, 73 
Clitoris, 195 
Cloaca, 194 
Coccyx, 28, 32 
Colliculus seminalis, 194 
Conus inguinalis, 196 
Cranium, capacity of, 51 



224 



THE STRUCTURE OF MAN 



Dental ridge, 161 
Descensus testiculorum, 196 
Diaphragm, 38, 177 
Diverticulum ilei, 165 
Duct, MuUerian, 189, 193 

Wolffian, 187 
Ductus Cuvieri, 184 

thyroglossus, 162 

Ensiform process, 44 
Epicanthus, 150 
Epididymis, 188 
Epiglottis, 173 
Epiphysis cerebri, 131 
Episternum {see Interclavicle) 
Eustachian tube, 150 
Eye, 147 
Eyebrows, 4, 150 
Eyelids, 148, 150 

Fallopian tube, 194 
Femur, 81 
Fibula, 83, 93 
Filum terminale, 124 
Finger nails, 1 1 
Fissura orbitalis, 148 
Fistulse, cervical, 172 
Foot, skeleton of, 85, 87 
Foramina, condylar, 78 
Fore-limb, skeleton of, 77 
Fossa, olecranon, 77 

orbital, 58, 148 

temporal, 58, 148 
Foveola coccygea, 5, 23, 28 
Frog, 11 
Frontal organ {see Paraphysis) 

Gartner, canals of, 189 

Genital duct, 189 

Gill clefts, 49 {see also Branchial 

pouches) 
Girald^, organ of, 189 
Glabella coccygea, 5, 23, 28 
Gland, coccygeal, 126 

pineal {see Epiphysis cerebri) 

pituitary {see Hypophysis cerebri) 

thymus, 163 

thyroid, 162 
Glands, genital, 196 

lachrymal, 149 

mammary, 12 

Montgomery's, 12 



Glands, nictitating, 149 
Glaser, fissure of, 65 
Great toe, 85 
Gubernaculum, 196, 197 
Gynaekomasty, 17 

Hair, 3 

tracts, 5 

vortices, 5, 23 
Hairs, tactile {see Vibrissae) 
Hairy men, 9 
Hallux {s6e Great toe) 
Hand, skeleton of, 79, 86 
Heart, 39, 180 
Hind-limb, skeleton of, 80 
Hip-girdle {see Pelvic girdle) 
Hottentot apron, 195 
Humerus, 77 

torsion of, 91 
Hymen, 194 
Hyoid arch, 65, 151 
Hypertrichosis, 7, 10 
Hypophysis cerebri, 135 

Ilium, 74, 76 
Incus, 64, 151 
Integument, 3 

sense organs of, 140 
Interclavicle, 46 
Intestine, 166 
Ischium, 71, 74 

Jacobson, organ of, 143 

Kidney, definitive, 188 

Labia majora, 195 

minora, 195 
Lamina papyracea {see Os planum) 
Lanugo, 9 
Larynx, 172 

musculature of, 174 

skeleton of, 66, 151 
Ligament, interclavicular, 48 
Ligamentum inguinale, 196, 199 
Ligula, 137 

Limbs, comparison of fore- and hind-, 
91 

displacement of, during develop- 
ment, 92 

disposition of, in adult, 9 1 

disposition of, in foetus, 85 
Limb girdles, 68 



INDEX 



225 



Limb skeleton, 67 
genesis of, 68 
Little toe, 89 
Liver, 38, 171 
Lobus olfactorius, 141 
Lumbar curvature, 32 
Lungs, 175 

Malleolus, fibular, 83 
tibial, 83 

Malleus, 64, 151 

Mammary glands, development of, 13 
supernumerary, 16 

Mammary line, 14 
pouch, 14 . 

Meckel, cartilage of, 64, 151 

Mesonephros, 187 

Metanepliros, 188 

Monotremata, mammary organ of, 
12, 14, 17, 198 

Mouth, development of, 136 

Muscle, adductor hallucis, 112 
agitator caudse, 99 
bi venter maxillse, 102 
cleido-occipitalis, 102, 112 
coccygeus, 98 
cremaster, 198 
curvator caudae, 27 
curvator coccygis, 99 
depressor caudse, 99 
epicranius, 107 
epitrochleo-anconaeus, 113 
extensor brevis digitorum. 111 
extensor carpi radialis, 119 
flexor brevis minimi digiti, 112 
flexor digit communis, 110, 117 
flexor digit. profundus, 110, 117,119 
flexor digit, superficialis, 110, 119 
flexor longus hallucis, 117 
flexor longus pollicis, 117 
frontalis, 107 
gastrocnemius, 120 
gemellus superior, 119 
gluteus maximus, 82, 99, 119 
ischio-femoralis, 114 
latissimo condyloideus, 112 
latissimo dorsi, 38 
levator claviculse, 114 
levator palpebrse, 148 
mylohyoid, 102 

opponens hallucis (and o. pollicis), 
88 



Muscle, opponens minimi digiti, 112 

orbi talis, 148 

palmaris, 109, 110 

panniculosis carnosus, 103, 113 

pectoralis, 45, 113 

plantaris, 109, 110 

platysma, 103, 105 

pyramidalis, 101 

pyriformis, 119 

rectus abdominis, 99 

semimembranosus, 120 

semitendinosus, 120 

serratus magnus, 45 

serratus posticus, 38 

soleus, 120 

sphincter colli, 106 

sternalis, 113 

subcutaneus colli {see M. platysma) 

transversus abdominis, 198 

transversus nuchse, 105 

triangularis sterni, 102 
Muscles, caudal, 27, 98 

cervical, 103, 113 

cutaneous, 103 

gluteal, 119 

intercostal, 43, 99 

interossei pedis. 111 

laryngeal, 174 

mimetic, 103, 109, 114 

of head, 103, 107, 115 

of limbs, 109, 116, 120 

of pinna, 107, 154 

progressive, 114, 121 

retrogressive, 98, 121 

scaleni, 102 

serrati, 98 
Muscular system, 97 
Myelon {see Spinal cord) 

Nails, 11 

Nerve, hypoglossus, 138 - 

trigeminal, 139 

vagus, 138 
Nerves, caudal, 32 

sympathetic, 139 
Nervous system, 123 
Nictitating membrane, 148 
Nose, bridge of, 61 

the projectile, 147 



Obex, 137 
(Esophagus, 164 



Q 



226 



THE STRUCTURE OF MAN 



Olfactory organ, 141 

Os acetabuli {see Bone, cotyloid) 

antiepilepticum, 57 

centrale carpi, 80 

fronto-parietale, 57 

planum, 60 

prseinterparietale, 57, 60 
Ossa suprasternalia, 48 

suturaria {see Bones, Wormian) 
Ossicnla auditus, 64, 151 
Ovary, 196 

Palate, hard, 63 
Palate, ridges of soft, 155 
Pancreas, 171 
Papilla foliata, 162 

palatina, 146, 156 
Paradidymis, 189 
Paraphysis, 134 
Parietal organ {see Pineal organ) 
Pectoral girdle, 68 
Pelvic girdle, 68 

development of, 74 

shifting of, 31, 95 
Pericardium, 38, 177 
Pineal gland {see Epiphysis cerebri) 
Pineal organ, 133 
Pinna, 108 

development of, 152 

muscles of, 107, 154 1 
Pituitary body (see Hypophysis cerebri) 
Platyknemia, 82 
Pleural cavities, 39 
Plexus, brachial, 95 

ischiadic, 95 

lumbo-sacral, 95 

pudendal, 95 

vesico-prostatic, 182 
Plica fimbriata, 161 

semilunaris, 148 
Polymasty, 17, 19 
Polythely, 17 
Ponticulus, 137 
Post-anal gut, 32 
Praeputium, 195 
Process, coracoid, 72 

paramastoid, 57 

styloid, 63 
Processus supra-con dyloideus, 78 

vermiformis, 167 
Promontory, of sacrum, 32, 34 
Pronephros, 187 



Pseudohypertrichosis, 9 

Pubis, 71, 74 

Pyramidal nerve tracts, 125 

Reditus testium, 198 
Respiratory system, 171 
Ribs, cervical, 41, 102 

lumbar, 39 

sacral, 40 

sternal, 45, 46 

supernumerary, 39, 44 

thoracic, 39 
Round ligament, 196 

Sacral dimple {see Glabella coccygea) 

Sacrum, 33, 40 

Scapula, 71, 72 

Scrotum, 198 

Sense organs, 140 
integumental, 140 

Shoulder girdle {see Pectoral girdle) 

Sinus, Morgagni's, 174 
venosus, 180 

Skeleton, 26 

Skull, 48 

Spinal cord, 123 

Spleen, 186 

Stenson, canals of {see Canals, naso- 
palatine) 

Sternum, 44, 46 

Stomach, 164 

Sublingua, 161 

Suprarenal bodies, 199 

Sutures, cranial, 55 
maxillo-palatine, 63 
premaxillo-maxillary, 62 

Sympathetic system, 139 

Tail, human, 5, 26, 31 

Tarsus, 79 

Teats, development of, 13 

supernumerary, 18, 20 
Teeth, ^esis of, 156 

milk, 160 

pre-milk, 160 

wisdom, 159 
Tegumental organs, 3 
Testis, 196 

descent of, 196, 198 
Third eyelid {see Nictitating mem- 
brane) 
Thorax, types of, 36 



INDEX 



227 



Thyroid cartilage, 66, 151 

gland, 162 
Tibia, 82, 93 
Tongue, 161 
Torus occipitalis, 57 
Trochanter, third, 82 
Tympanic cavity, 150 

Urachus, 181 
Urinogenital system, 187 
Uterus, 194 
Uterus masculinus, 189 

Vagina, 194, 195 
Vas deferens, 188 
Veins, intercostal, 186 

posterior cardinal, 184 

valves of, 185 
Velum medullare, 137 
Vena cava inferior, 1 84 



Vena cava superior, 185 
Venous system, 184 

anterior abdominal, 182 
Vertebrae, caudal, 31 

coccygeal, 27 

thoracic, 43 

sacral, 33 
Vertebral column, 26 
Vertex coccygeus, 5, 26 
Vibrissae, 4 

supra-orbital, 150 
Visceral skeletal arches, 49, 64, 66, 

151 
Visual organ (see Eye) 

Whiskers {see Vibrissse) 

XiPHISTERNUM, 45 

Yolk sAqJ^ 



THE END 



Printed by R. & R. Clark Limited, Edinburgh. 






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